Don't split the party! I mean split the party!

I found a new example of forced party splitting in Fane of the Night Serpent which strikes me as just too odd. Upon encountering Celeste, she says something (because what she says is not found in Chat Logs...) like, "Go on ahead, I'll free these prisoners." Upon hearing this suggestion I decided to search the room from which I saw her emerge in the cutscene. Then, go back to check on Celeste. I don't know what she's using to try to unlock the prison cells but she never gets one open as I decided to wait for her in case she can't handle the red wizards and also because I don't know what I'll encounter next. But, after waiting for several minutes, it seems Celeste will forever try to unlock the cells and with no means of interacting with her, I can't even talk to her or ask if I can do it since she seems incompetent.

Then, after killing all the critters I can access in the next room I go back to check on Celeste and she's gone. The prisoners in the cell she was "trying" to free are still in there.

Then, I backtrack the entire map and still Celeste is nowhere to be found.

Then, after I successfully defeat Fenthaza, Celeste walks in calmly with some words.

Overall, totally confused by this quest.