This is something that I've had to deal with a few times, on the other end, I grew up middle-upper class and dated whoever.

I always hid my life and background from them until I felt comfortable. But I'll never forget there was one time where a miscommunication blew up into something insane because of an insecurity that she had in the back of her head about me. I don't care where people came from, as long as we're both on the same page working on the same goals, but there is an insecurity that can come up, like it seems to have for you with her and this comment.

It was over the fact that I wasn't familiar with value brand items in this grocery store I wasn't familiar with and only grabbed name brand. She automatically assumed I was so rich that we always paid for name brand things instead of the value brand but what she didn't stop to ask or find out is that that actually wasn't the case at all. I just didn't want that particular great value item because I had tried it before and didn't like it. There were other great value stuff I bought all the time and liked. My family didn't even go to any stores for grocery as we lived out in rural IL and went to Amish farms for most of our goods... so it had nothing to do with me turning up the nose, but it told me right then and there how she saw me, whether she said it out loud or not. She had called me a spoiled brat before I even had a chance to explain anything and was so shocked and insulted I just walked right out of the store without a word.

So I feel like if you can't let this kind of stuff go, y'all better off walking away from each other.

The relationship ended thereafter, for that and other reasons, but I find that when there is a deep insecurity there, whether it's the person that may have come from more or the person that came from less - it never tends to work out. People should feel comfortable about who they are, where they came from and where they're going. Not every stupid comment is somehow twisted into revealing your preconceived notions of people coming from more looking down on those coming from less or vice versa.