How much age gap is creepy?

I was born in 1998. I was talking to a girl in the club, it was obvious to me that she’s younger than me, but I didn’t ask her age. And then we saw one of her friends and she was saying that this girl is amazing and bla bla bla and she turned to me and said “and also she’s very young, you know that? She’s only 21.” I felt really bad and felt like a creepy man afterwards, specially with the way her friend mentioned her age. I really thought she’s like 23 ish. But I really liked her, and I keep thinking about her. But I don’t know if this age gap is creepy or not? Am I no better than creepy men? 😭