I’m not autistic, just ADHD, so please stop me if I’m invading a space where my commentary isn’t welcome.

You didn’t recognize that the girl in question was setting boundaries, which isn’t your fault, but I’ll get back to that in a minute. From her perspective, she made it clear that she wasn’t interested in you romantically, but she felt like subsequent actions still had romantic intent, like spending a lot of time near her and chatting. The way she was communicating with you wasn’t working, so she tried asking a friend to find an alternative resolution. I don’t want to get into the details of defining what “creepy” might mean to different people, but what’s important is that she felt unheard and wasn’t able to influence her environment to meet her needs. And that sucks for anyone.

Autism makes it hard to understand subtler forms of boundary setting, but you can totally learn how! I had a poor time understanding and respecting boundaries because throughout my whole childhood, my boundaries were never respected, nor were anyone’s boundaries in my childhood environment, so I never learned. And the things I implicitly learned where downright harmful. I may be projecting a bit, but I suspect you have a difficult time both setting and respecting boundaries because you haven’t been taught. Personally, I loved the book (or audiobook) Set Boundaries, Find Peace by Tawwab. It walks through a bunch of conversation examples regarding setting boundaries, which my autistic brother said is super helpful.

https://www.amazon.com/Set-Boundaries-Find-Peace-Reclaiming/dp/0593192095