AITA for telling my girlfriend to keep her nose out of my friend’s business?

One of my older friends (he’s 26 now, turning 27 in a few months, rest of our friend group is 20-22), Sam, is planning to come with our friend group to our skiing lodge trip over winter break between semesters. This last trip is very important to him, his wife is having a baby and it’s not likely he’ll be able to continue to go even though we plan to continue it after we all graduate. Now keep in mind the due date actually isn’t even 2 days until after he would be getting back, not that it matters because their marital affairs are literally none of our business.

As you can imagine his wife is upset with him over this. That’d be fine except my girlfriend has become friends with the wife so now I also have to hear about how wrong it is for him to be leaving during this time. Sam approached me and my other friend about the rude comments our girlfriends have made towards him about him “abandoning” his wife, and I’ve apologized profusely for her behavior and told him I’d address it.

I told my girlfriend that she was out of line, that how Sam wishes to handle his domestic affairs is up to him, and that she needs to keep her nose out of it. I told her it was totally unacceptable how she was butting into their affairs, even if nominally doing so to defend the wife. She said that I’m not in control of her, she’s free to speak her mind, and I can’t tell her what to do. I rightly said that she can’t tell my friend what to do either, and that there’s a certain amount of expectable tact from a partner and that it was totally unfair of her to be hostile to a close friend of mine thus putting me in an embarrassing situation like she has done.

AITA or is my girlfriend for placing me in such an uncomfortable situation by butting into other people’s business?