Interesting start.
I would defintiely stick to a max spell level of 6th. These girls are way too heaviliy armed to not. Drop the spiked chain - that's giving them a free combat feat and that's really gonna eat into the balance for other things that are more in keeping with the idea. It generally looks like it's comming together as a divine bard (not a bad comparison really). Using the same BAB and saves as a bard is probably fair. They aren't spontaneous casters, but they'll probably have a better spread of class abilities than the bards performance tricks. Despite being divine casters, I would have them suffer armor spell failure as they normally seem to be dancers when casting which just doesn't look good in full plate

. Make a choice on which stat they use for spell saves rather than the choice they have now. Then use the other stat for how many bonus spells they get. I tend towards Cha for saves and Wis for bonus myself. Split stats like that were used quite a bit in the Minitures handbook and they worked well.
Skills should be followed by key ability as follows~
The Miko’s class skills are Balance (Dex), Concentration (Con), Craft (int), Diplomacy (Cha), Handle Animal (Cha), Heal (Wis), Jump (Str), Knowledge (arcane) (Int), Knowledge (nature) (Int), Knowledge (religion) (Int), Listen (Wis), Move Silently (Dex), Perform (dancing/singing) (Cha), Ride (Dex), Sense Motive (Wis), Spellcraft (Int), and Spot (Wis).
Simplify the wording of Divine Favor~
Divine Favor: The multitude of gods and goddesses that look over the Miko protect these shrine maidens even beyond death. When a Miko dies there is a (5% + 1%class level) chance that she receives the benefits of a
resurrection spell the following dawn. If the Miko dies on the holy grounds of a shrine, this chance increases by +10% (to a maximum of 25%).
Lock touch Mastery down as allowing them to use Cha instead of Str for touch attack - this fits with the perform skill. I like the idea tough, as it gets them away from needing strength.
I would tend to think they should get Craft Wand, as they are often shown with them (with ofuda tide on the end, but a wand nonetheless). Maybe not at 5th level, but at some point. Wand master (from Eberron) would also be good at higher levels - thematicically fits well with their rituals.
High levl also might offer some bonuses to save vs. death effects and resistance to level drain. Other than that they need a spell list but look pretty good

.