Hi,

See my previous thread on this issue. This is a bug and is somehow related to having her join your party during the fights with Thorm.

https://forums.larian.com/ubbthreads.php?ubb=showflat&Number=956928#Post956928

What I ended up doing was going back to just before the fight at the Tower. When she asks to join the fight, I decline. Once I finally have a camp in Act III I could then add Jaheira to my party and she was considered an "ally" for purposes of spells and combat. So things seem to be working correctly now.