I'm acquainted with Barb Fast. I've worked for her as a soldier and as a contractor. She was not promoted out of political considerations. She is one of the few senior MI officers I've dealt with that is competent with details, decisive and not a micromanager. Nobody's perfect but you won't do much better than Barb Fast.
I take you at your word that she is a good leader. However, as we all know, at the senior level, nuance, timing, and political connections are extremely important. Her association with the Abu Gharib prison has tainted her. Rightly or wrongly, she will never go any further.
I know there must be some good women general officers. Claudia Kennedy was another lousy choice for promotion, but I'll take your word on Fast.