I don't think it's be super-difficult to give her what she wants by making it up as you go along.
Step 0: accept that a well-build 3e druid can do anything and is probably overpowered. Accept that you're not planning to perpetuate that design mistake by creating an unbalanced class.
Step 1: get the 4e core books.
Step 2: look up the MM gnome; IIRC the gnomes are expected to get a writeup in the "monsters as PCs" section of the book. If not, pull out some common things from the Gnome monster entries, choose stat modifiers (+2con/+2int is probably appropriate), and merge them with the small size stuff from the halfling. Either way, you'll have a Gnome race entry.
Step 3: Choose a role for your Druid class. This is probably the most important decision, as it gives you the overall "feel" of the class. Try to resist the temptation to make a character that can fill multiple roles; if you do, you'll have trouble keeping the class balanced, and you won't have a clear power list to model yourself on. Note that this doesn't mean that all Druids in your game will have this role - perhaps it's a specialty of just your druid.
Step 4: Create your shtick. This is how your particular class mechanism works. Look at what differentiates the other classes with the same role as you, and pick something that's similar. For example, all the Defenders get some kind of Mark ability, so if you're making a Defender, you'd also need some Mark mechanism. That forms the core of your class abilities.
Step 5: Write the rest of your class abilities based on the other classes with your role.
Step 6: Define your starting powers such that they have similar, but not identical effects to the powers at the same level for other classes with your role.
Here's an example for steps 3-6: Say you wanted your Druid to be a Striker. All of the other Strikers get extra damage schticks. Yours might be:
Feral Form.
Encounter power
Minor Action - Animal - Stance
Target: you
Effect: you enter Feral Form. While in Feral Form, your equipment has no effect, and you may not speak or use non-Feral attacks or powers. You are treated as though wearing Hide armor, and you have an enhancement bonus to AC, melee attack rolls, and melee damage rolls equal to 1/5 of your level, rounded to the nearest value. Your Strength score becomes equal to your Wisdom score. You become a Medium creature if you were not one already. You may leave Feral Form as a Minor action.
Nature's Ferocity
Once per round, you may increase the damage of a Feral attack to one target by 1d6. This increases to 2d6 at 11th level and 3d6 at 21st level.
After that, the rest of the abilities pretty much write themselves:
Armor prof: cloth, leather, hide
Weapon Prof: simple melee, simple ranged
HP, healing surges: as Ranger
Trained skills: Nature, plus four from this list: Athletics, Endurance, Heal, History, Insight, Perception, Religion, Stealth
As for Powers:
Pounce - Druidic Striker Attack 1
At-will - Feral
Standard action
Requirement: Feral Form
Target: one creature
Special: you may shift two squares before you attack, but each shift must take you closer to your target.
Attack: Str versus AC
Hit: 1d8+Str damage
You leap onto your target, claws flashing.
(Design: Rogue's Deft Strike)
Crushing Bite: Druidic Striker Attack 1
At-will - Feral
Standard action
Requirement: Feral Form
Target: one creature
Attack: Str versus Fort
Hit: 1d8 + Str damage; damage increases 1d10+Str at 11th level and 1d12+str at 21st level.
Your jaws close around your opponent, crushing armor and flesh alike.
(Design: Rogue's Piercing Strike)
Towering Fury: Druidic Striker Attack 1
Encounter - Feral
Standard action
Requirement: Feral Form
Target: one creature
Attack: Str vs AC
Hit: 2d8 + Str damage. and target has -2 to all defenses until the end of your next turn.
You rise on two legs and rain blows on your opponent in a terrifying display of nature's fury.
(Design: Warlock's Witchfire, kinda)
Claw Frenzy: Druidic Striker Attack 1
Daily - Feral
Standard action
Requirement: Feral Form
Target: two creatures adjacent to you
Attack: Str vs AC; Make 2 attack rolls and apply the highest to both targets
Hit: 2d8 + Str damage
(Design: Ranger's Split the Tree)
Then at 2nd level, you might get a utility power like:
Bond of Life
Daily
Standard Action
Target: one ally
Special: not useable in combat
Effect: Ally gains HP as though he had spent a healing surge. You gain HP equal to his Con modifier plus your Con modifier.
Or:
Squirrel Form
Daily
(like Feral Form, but you're Tiny, your Dex is equal to your Wisdom, you only get the enhancement bonus to AC, and you get +2 to Stealth and climbing checks)
Step 0: accept that a well-build 3e druid can do anything and is probably overpowered. Accept that you're not planning to perpetuate that design mistake by creating an unbalanced class.
Step 1: get the 4e core books.
Step 2: look up the MM gnome; IIRC the gnomes are expected to get a writeup in the "monsters as PCs" section of the book. If not, pull out some common things from the Gnome monster entries, choose stat modifiers (+2con/+2int is probably appropriate), and merge them with the small size stuff from the halfling. Either way, you'll have a Gnome race entry.
Step 3: Choose a role for your Druid class. This is probably the most important decision, as it gives you the overall "feel" of the class. Try to resist the temptation to make a character that can fill multiple roles; if you do, you'll have trouble keeping the class balanced, and you won't have a clear power list to model yourself on. Note that this doesn't mean that all Druids in your game will have this role - perhaps it's a specialty of just your druid.
Step 4: Create your shtick. This is how your particular class mechanism works. Look at what differentiates the other classes with the same role as you, and pick something that's similar. For example, all the Defenders get some kind of Mark ability, so if you're making a Defender, you'd also need some Mark mechanism. That forms the core of your class abilities.
Step 5: Write the rest of your class abilities based on the other classes with your role.
Step 6: Define your starting powers such that they have similar, but not identical effects to the powers at the same level for other classes with your role.
Here's an example for steps 3-6: Say you wanted your Druid to be a Striker. All of the other Strikers get extra damage schticks. Yours might be:
Feral Form.
Encounter power
Minor Action - Animal - Stance
Target: you
Effect: you enter Feral Form. While in Feral Form, your equipment has no effect, and you may not speak or use non-Feral attacks or powers. You are treated as though wearing Hide armor, and you have an enhancement bonus to AC, melee attack rolls, and melee damage rolls equal to 1/5 of your level, rounded to the nearest value. Your Strength score becomes equal to your Wisdom score. You become a Medium creature if you were not one already. You may leave Feral Form as a Minor action.
Nature's Ferocity
Once per round, you may increase the damage of a Feral attack to one target by 1d6. This increases to 2d6 at 11th level and 3d6 at 21st level.
After that, the rest of the abilities pretty much write themselves:
Armor prof: cloth, leather, hide
Weapon Prof: simple melee, simple ranged
HP, healing surges: as Ranger
Trained skills: Nature, plus four from this list: Athletics, Endurance, Heal, History, Insight, Perception, Religion, Stealth
As for Powers:
Pounce - Druidic Striker Attack 1
At-will - Feral
Standard action
Requirement: Feral Form
Target: one creature
Special: you may shift two squares before you attack, but each shift must take you closer to your target.
Attack: Str versus AC
Hit: 1d8+Str damage
You leap onto your target, claws flashing.
(Design: Rogue's Deft Strike)
Crushing Bite: Druidic Striker Attack 1
At-will - Feral
Standard action
Requirement: Feral Form
Target: one creature
Attack: Str versus Fort
Hit: 1d8 + Str damage; damage increases 1d10+Str at 11th level and 1d12+str at 21st level.
Your jaws close around your opponent, crushing armor and flesh alike.
(Design: Rogue's Piercing Strike)
Towering Fury: Druidic Striker Attack 1
Encounter - Feral
Standard action
Requirement: Feral Form
Target: one creature
Attack: Str vs AC
Hit: 2d8 + Str damage. and target has -2 to all defenses until the end of your next turn.
You rise on two legs and rain blows on your opponent in a terrifying display of nature's fury.
(Design: Warlock's Witchfire, kinda)
Claw Frenzy: Druidic Striker Attack 1
Daily - Feral
Standard action
Requirement: Feral Form
Target: two creatures adjacent to you
Attack: Str vs AC; Make 2 attack rolls and apply the highest to both targets
Hit: 2d8 + Str damage
(Design: Ranger's Split the Tree)
Then at 2nd level, you might get a utility power like:
Bond of Life
Daily
Standard Action
Target: one ally
Special: not useable in combat
Effect: Ally gains HP as though he had spent a healing surge. You gain HP equal to his Con modifier plus your Con modifier.
Or:
Squirrel Form
Daily
(like Feral Form, but you're Tiny, your Dex is equal to your Wisdom, you only get the enhancement bonus to AC, and you get +2 to Stealth and climbing checks)
