What would you do?

"What do you mean by that?"

Or, I'd just ignore her.

Don't get in between your nephew and this...person.

It will turn out to be a fluke, a misunderstanding on her part, or a really painful future lesson for your nephew.

Very good answer.

I would also say the girlfriend was as rude, inappropriate and psycho as can be. Even if the aunt was a "gold digger" that should not be the first thing you say to someone you have just met, particularly if that person is the aunt of your boyfriend.

Very sorry you experienced this. With the way society is now I have close to zero tolerance for this. I like to give the benefit of the doubt but usually it does not serve. I would also have to consider if the relationship and family members are worth it.

Another excellent answer.

Yes, you have to wonder why the nephew and family would continue to to have a relationship with the girlfriend.

Couple things come to mind. One is what’s called Maslow’s hammer, it says "If all you have is a hammer, everything looks like a nail.” So maybe I’d feel sorry for her if that is all she’s got in her skill set.

The other is from a book I’m reading by Mel Robbins, the Let Them Theory. She suggests when someone does something like that you just “let them”. Actually brings you back in control because you’ve chosen to just let them say what they want. People will say all kinds of things, sometimes hurtful sometimes crazy. Let them.

I have a very different response about this.
When everyone is seated for dinner, I would bring up a situation that ‘happened’ recently. I’d say that “I was out for dinner w/friends and one friend brought along another person, someone none of the rest of us knew. Anyway, one of the women (we’ll call her Jane) excused herself to use the restroom, and while she was gone the new person called her a gold-digger. The rest of us were shocked, and we admonished her for the negative comment, and we wondered how she could form such a negative opinion of Jane having only barely known her.” Then look at your nephew’s friend and politely and innocently ask “What do you think would cause someone to say that?!?”
I am certain she would get your message…
Then you can put it to rest.

Thanks but I wouldn't play games like that. Personally I think the best response is to say and do nothing. Just let it go. In the future if this woman behaves in a similar fashion, and she most likely will, then she will suffer the consequences. If the family continues to have a relationship with the woman then I would consider my relationship with the family.

But what I would really like to do is say "You need to leave now!".

@robertwills Odd behaviour of someone who has never met you before, and who has no relationship to you in any way! This time I would ignore the comment. If such behaviour is repeated, I would ask her point blank why she has this opinion about you. If her behaviour continues, I would talk to the nephew’s mother and tell her if this woman continues to insult you like this you will not be attending any gatherings where she is present, and leave it at that.

Yes, I agree with that course.

Yeah, I'd say something to her. I'd say, "Excuse me? Do I know you? You must have me confused with someone else! And, you need to learn some manners!"
Then, I'd tell the nephew what she said. He needs to know this aspect of her personality.