You know as much as me that faith is believing... but I should have said "former faith" since she apparently lost it along the way.
I know nothing about schizophrenia... did a little AI searching but can't speak authoritatively. Scriptures promise a chance at healing with the Lord but not guaranteed (unlike that TWI hand that always fits in the glove, we know healing is not always the end result).
But first, I would do everything medically in the senses realm... medication, therapy, etc. While seeking that, continuing in prayer (and fasting) and wait for a response from God. We know God allows these things to occur -- the biggest question is why? I don't have an answer to that, but the fact that I don't doesn't stop me from continuing to have faith in him.