Hmm, haven't tried saving and reloading after levelling and checking her spellbook, gonna give it a try when I get home and report back.
The greyed-out-effect: she takes damage during the introduction fight, asks to join the party, I accept and her HP is 1/10, at level 0. Now if I level her up like this her max HP falls to 4 HP and then appears greyed out. However if I heal her to full health then it's ok.