My [30F] girlfriend's friends make fun of her for being too stingy. Laughed at first, now it's getting a bit annoying.

My girlfriend and I have been financially independent since we finished college, we work a lot and at first, we struggled financially. Right now, we're doing better, but we're not rich or anything like that, just enough to have a more relaxed life. We both are careful with money, for example, we buy low to medium priced food, but in other areas (clothing, computers) we do spend from time to time, mostly on high-quality items. We also have money funds for emergencies, for summer holidays etc.
When her friends saw some "stingy" behavior ( for example buying stuff from cheaper stores a long way from home) they made jokes about it and at first, it wasn't a big deal, but it is getting annoying, also because we have helped them with small money loans in the past.
I must say, it's not a big issue or anything, but how can we put an end to this behavior in a light-hearted way?
TLDR: Me and my GF are a bit stingy with money, but never towards our families or friends. Some of them are making fun at our expense, how can we diffuse the situation?


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