M Y S T I
and i got smarter i got harder in the nick of time
Every Touhou game only consists of female characters (unless you count a wise old turtle, a girl's pet cat, and a cloud spirit who have very minor roles), and the games are all free off the Moriya Shrine website. If you have even a quarter-decent computer, you can easily run these games. Unless you're willing to practice bullet hell, though, I'd recommend Touhou 10.5: Scarlet Weather Rhapsody or Touhou 13.5: Hopeless Masquerade.
Bullet Hell is fine, if you've played Undertale. And seeing local cryptid 's profile picture of Undyne (I assume, maybe my eyes are defying me as its 3aM) I assume they've played Undertale. And Undertale's main character, Frisk, can be male or female, depending on how you depict he/she.
I also suggest Horizon - Zero Dawn. My boyfriend just got it, and he's been obsessed. Aloy is a really strong character, I think you'll like it. Fair warning, the game Horizon Zero Dawn costs $80, plus the DLC which is supposed to release soon. Plus Horizon is an open-world, leaving you and Aloy chances to appreciate the really well-done scenery and lighting.