I'll add some people when I get home from work.
44.
Cailet Ambrai (Melainie Rawn's Exiles)
Cailet became Mage Captal at the age of 17, when her dying predecessor -- and two other Mages with little time to live -- transferred his knowledge of magic (and some other things) to the powerfully mageborn third daughter of Maichen Ambrai and Auvry Feiran.
She was the magical force behind a successful revolution, and battled afterwards to keep the Mage Guardians apolitical. She had less success there, and as of the conclusion of Mageborn Traitor, is in hiding.
45.
Moiraine Damodred (Robert Jordan's Wheel of Time)
When Moiraine and her best friend overheard the birth of the savior -- and destroyer -- of the world being prophecied, as her arcane training was coming to a close, she began a quest that would claim her life in finding the boy who would be the Dragon Reborn, and teaching him as much as she could of what he needed to know.
She sacrificed herself to kill the Forsaken Lanfear, a much more powerful weilder of the One Power than herself.
46.
Susannah Dean (Steven King's Dark Tower)
Other names that come to mind...
Jean Grey (X-Men)
Rogue (X-Men)
Storm (X-Men)
Winifred 'Fred' Burkle (Angel)
Faith the Vampire Slayer (Buffy/Angel)
Willow Rosenberg (Buffy/Angel)
Cordelia Naismith Vorksosigan (Lois Bujold's Vorkosigan saga)
Eli Quinn (Lois Bujold's Vorkosigan saga)
Aliera e'Kieron (Seven Brust's Dragaera)
Esmeralda 'Granny' Weatherwax (Terry Pratchett's Discworld)
Susan Sto Helit (Terry Pratchett's Discworld)
Althea Vestirt (Robin Hobb's Liveship Traders)
Hermione Granger (JK Rowling's Harry Potter novels)
Lina Inverse (The Slayers anime)
Apsalar (Steven Erickson's Mazalan books)
Nynaeve al'Maera (Wheel of Time)
Egwene al'Vere (Wheel of Time)
Elayne Trakand (Wheel of Time)