Hi Ptr, two books.
Don't worry, they'll go fast.
for you
"Controlling cult mind control" by Steve Hassan will make you understand what you're up against.
for her
"Crisis of conscience" by Ray Franz.
Ask her to look at it before committing her life,tell her that you just want what's best for her and you want her to make an informed decision about something that will greatly effect her and everyone else around her.