How can I make my gf less uncomfortable about the age gap between us?

(Sorry if this isn’t the right place for a question like this)

So me and my gf have a 7 year age gap with me being 21 and her being 28 I meet her when I barley out of college and applying for jobs and I just happen to apply where she worked. We’ve been dating for 9 months now and I’m very much happy with her and love her very much not just because I think she’s beautiful but also because of how honest and mature she is not that I’m into more mature woman.

I’ve never had a problem about our age gap mainly because I never really gave much thought about it but she always been a bit weirded out by it she always insist that we stay in for dates, avoids age related conversations and always saids that we should keep our relationship to ourselves.

It’s always been somewhat weird to me that she makes it a big deal so a week ago I decided to just ask her and she proceeded to say that she worried about how other people would perceive the relationship between us. That others might think that she or I’m taking advantage of one another, if I would leave her for someone younger, and how a long term relationship would be like. She also saids that she kinda gets embarrassed when her friends make jokes about the age gap obviously she knows there just jokes but still.

I think she saw I was concerned about what she said so then she tried to reassure me saying that it’s not a deal breaker for her that I’m younger and that she genuinely does like me. it’s just that she doesn’t really know how to go about the relationship since she’s never dated someone younger.

I honestly don’t really know what I can say or do to make her comfortable about the age gap since I’ve never been in this type of relationship. Obviously I do love her and want to be with her even with the age gap.