Why are some people like this with my relationship?

I have a friend who keeps criticizing my relationship because my boyfriend is in his 30s. She has always called him gross and that I should be dating guys my age like she does but she hasn't had a stable relationship in forever she's had like 4 boyfriends in 6 months and I've been with my boyfriend for over a year with no issues. I just dont see why some people have to shame our relationship because of the age gap. Why are people like that? Is it maturity or jealousy or something else?

Why are some people like this with my relationship?
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