Male Chara x Female Reader

What if in this universe Chara didn't go genocide and Asriel didn't turn into Flowey? Both boys grown up to be 18 with the monsters, till Frisk(who is a year younger than Chara and Asriel) showed up and started living with in the monster realm as well never opening the barrier at all.
Y/N was running away from her foster family, she had enough of their abuse and ran away when school ended. Y/N was running to the woods where Mount. Ebott was and while getting there and climbing up the mountain she acidentally fell from fatigue into the deep abyss.

You guys will have to find out by reading this story (p.s. this is my first ever x reader book so be kind to me ^///^)
Disclaimer: I don't own Chara or any characters from the video game Undertale