Why do so many girls refer to their friends as “girlfriends”?

I hear people say this all the time, and it’s so weird to me. I’m a girl and I would never refer to my friend as my girlfriend. Girlfriend means dating, does it not? It’s not that big of a deal, but it always bothers me when I hear it, why can’t they just say “my friend”, “my bestie”, or “my best friend”?