I’ve said it before and I’ll say out again. If people are really going to look down on you because you were born into a family that isn’t making as much as other people, don’t try to gain their approval. Find true friends who will love you for who you are and not the superficial ones who look at money and status.
Eh, while true and I agree, that moralistic stuff doesn't stop it from hurting. Same way "don't stoop to your bullies level" or whatever doesn't
really solve the problem for you. She had a (percieved) problem and worked to fix it.
Plus she's at a real tender time in life where social relations & image matters maybe even more because she's a girl.
Maybe this experience is what will drive her as an adult to work hard & not be poor or dress well.
Basically what I'm trying to say is while I agree on your point her reaction on the matter is reasonable.
People want to be validated, people want to be included, people want to feel good about themselves, not just deal with the reality.