Ok, I'm going to go WAY simple and say maybe she just really doesn't like giving blow jobs. Why do we insist on complicating the facts with a round of “let’s psychoanalyze the wife” instead of looking at the possibility that she just doesn't like it? If the subject was another sexual act, something less "mainstream" and she didn't like it, would you be looking for deep reasons as to why? I think you would just accept the fact that she doesn't like it and move on to finding things that you both enjoy. The fact that she was embarrassed about squirting may have nothing to do with not liking blow jobs and perhaps she said she felt having cum in her mouth was "demeaning" just to get you to stop trying to get her to do what she wasn't interested in doing. Not everything we choose to do or not to do is a response from some traumatic childhood experience. Just a thought...
And, if you are eager to have a blow job to completion, find a playmate that enjoys giving them. Problem solved