She has an intense personal dislike of Trump as politician, and appears to live and breathe politics. At any rate, I'm inclined to follow your lead, that she acted on her own. The details of her personal motivation aren't all that important.
I bet that her “boss” isn’t all that happy with her right now.
In politics, perception is reality. The fact that she is associated with Jeb communicates the perception that he and/or his campaign engineered her appearance at Trump's function and this whole thing blew up in the Bush campaign's face. The perception is that the Bush campaign is feckless and can't shoot straight. It reminds people of the Bush campaign crop duster that flew over the stadium at Trump's campaign rally.