Usually going back to ACT I has a tendency to break not just her, but Halsin as well even if they're not in the party. But you are quite correct that it seems to be an issue.
Yes, you're right, just tested it without going to Act 1 after recruiting her and there's no issue. Annoying to be stuck with this in my newest playthrough though as I did not know that could happen and I'm already in Act 3. *sigh* There's a pretty big chance to end up with this bug if you go the Underdark route to Act 2 and then Lae'zel forces you to go to the crčche.
And while testing I found a new bug. As soon as you walk into the Moonrise Towers throne room for the first time Minthara runs up to you, drags you into a dialogue cutscene and throws the "When you are done, we will celebrate our victory at your camp." line at you.
