She has a heal spell that is single use unless it is memorized. Her mage book screen is grey so I can't manipulate it. Is she just worthless or am I doing something wrong?
It's been a long time, but I believe in Baldur's Gate there's a distinction between "Mage Spells" (which are in the mage book) and "Priest Spells" which are in the Priest scroll.
Have you checked her Priest scroll?