Is 17 and 15 bad?

Pls don't judge me too much.

I'm 17m. A few days ago I started talking to a girl online, I had the impression she was also 17, but she told me she's actually 15 and turning 16 in a couple of months. I asked some friends and they told me it's not creepy or weird and this age gap is actually fine, but it's still feels pretty yucky to me so I need to know if it's really as bad as I feel it is.

Thoughts?