Okay, some of the dev’s have been a bit cagey on this subject. I mean to me it an open and shut case. She would have went rampant long before Cortana’s plan and had no means of accessing the Domain herself. Also Tales from Slipspace states that she was going to commit final dispensation.
I personally think it would be a mistake to not show her commit the final dispensation and kill herself. For one thing, it would be a good way of saying farewell to a character instead of killing them offscreen. Also, its pretty pertinent thematically to the whole Created storyline. They have said that this is a Going Concern in their universe and that its relevant to Isabels storyline. So, it would make sense to contextualize why so many AI join Cortana and the very real temptation Isabel would have if we see this AI have no choice but to destroy itself in the opening scene. I think showing that would be quite a powerful way to open the story and set this quite fatalistic tone.