I’m 21 she’s 18?

Started seeing this girl, get on really well knew each other for a while and we do like each other, lot in common and after gettin to know her she is mature for 18. however I feel abit un easy about the age gap for some reason, I turn 22 in may and she’s 19 in early October, is this bad?
I’m 21 she’s 18?
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