Sorry to hear it didn't go well; it does sound like there were some awkward dynamics in play, maybe for all of you.
So much of it depends on what everyone's expectations are about being poly in general, being involved with someone who is, and what the intent of the meeting was for. If you and she (and maybe he) both felt that she was there to "interview" you and decide if she wanted to exercise her veto, then, yeah: that's a tough current to swim against, even if she decided not to.
I hope you're not feeling too down about it and at least can find some time to process the encounter with him.
I do just want to add: not everyone's definition of (or need for) a "veto" is the same. While I understand why many wouldn't want to be involved at all with anyone whose partner had some kind of veto, I don't think the existence of that agreement between two partners should necessarily be viewed as a negative in and of itself. It all comes down to what everyone directly involved finds they can be comfortable with.