I need some help, I'm scared.

Ok, so I've been friends with this girl for a while since we were like kiddos, but she told me that she was lesbian, and I was like, "Oh cool cool", I'm a female btw, but then I invite her to the movies and we hang out, and she starts to flirt, and me being totally clueless, just flirts back and laughs thinking it's some joke, well weeks later somebody tells me that somebody likes me, and I'm like "Oh sweet", turns out, it's me, friend. I've don't want to be in a relationship, I don't even want to do anything romantic, I don't know how I should tell her this, I don't want to let her down, because this was the first time somebody has had a crush on me. Like poggers that I won't die a virgin, but like, I kinda don't want to ever be a non-virgin

I'm scared plz help.