How to help my player have more fun. GM here. 

I have a player in my campaign playing a dreamspun sorcerer. The problem is... my plot is very undead-centric. Undead being immune to mind effects has her feeling... less than useful. Just today I offered her a character mulligan, but it feels bad man. I want to allow her to play the character that she wants while still having fun. I don't want to have to throw out the master plot that I've written but I also don't want to make her do something that she won't enjoy. 

What advice does the pathfinder hivemind have for me?