If two people met and they were underage but one turned 18 then asked the other out that was still not 18 would that be ok?

I (18m) met a girl that was apart of my friend group one and a half years ago (I was 17 and she was 15) she’s now 16 and I realize now I might have had feeling for a while and we’ve become really good friends over the summer

Would it be weird or illegal if I asked her out? Or should I wait till she’s 18 which would make me 20? Or is that weird/illegal?

Ps: I absolutely do NOT intend anything sexual until after she’s 18