I dunno, it always seemed to me Crosby got out of Trek as quick as she could and then spent the time since doing her best to get back into it. Her reasoning behind that seemed a bit vague, but mistakes happen.
It was interesting to learn she did inquire about Nemesis. More interesting to say they couldn't find a place for her. You could've subbed in Sela for Donatra and really wouldn't have had to change her lines. Heck a half-human Sela hitting on Shinzon would make a twisted kind of sense.