The one thing in your post that I saw that was potentially problematic is when you said that she's gorgeous and you'd never know she was born a man. I get what you mean and in context I understood your intention in saying that. However, that could be hurtful to her. Sort of like if you're talking to a person of mix race and say, "I would have never guessed you were X race! You seem so intelligent!" I get I'm not comparing apples to apples here, but it was the best way for me to show how that could be seen as problematic.

I'm in HR and I've had to give SO MANY trainings to my employees on how to accept and behave around trans co-workers and employees, so that's why I totally understood your questions. I also work with people and oversee people from multiple generations, so I'm actually insanely proud of you for being accepting of her in that way and putting your son's happiness in the forefront here. I also completely understood your concern about your husband. I wish all of my employees started from the same place you are (just needing a little bit of adjustment, but overall accepting) because my life would be so much easier (instead of having to deal with people...typically your husband's demographic...who would insist on calling your son's GF "he" or constantly, purposely deadnaming them...don't get me started on that this early in the morning LOL).

It's new territory for you and new territory can be a bit daunting, but as I tell my employees, "It's really simple: Just don't be an asshole." (I don't think you're an asshole, but that's the blunt way of saying, "Treat everyone like a human being and adjust up or down where needed.")