why do girls call guys best friend?

Vague title I know, but what I mean is why do girls start calling certain guys they just started talking to (about a few days or so) best friend, there are two girls in my life who just became my "friends" they both think I'm cute and both think I have a great personsality and mentality and think that I'm different and weird, the one girl L I have been talking to a bit longer than n and so she's already talked about cuddling with me and has complimented me on my body and asked for a pic pf my abs and thinks I have a pretty smile, and om pretty sure she wants to show me her boobs, ( I know by how she talked about them in a random conversation) while the other girl, N hasn't been orthography with mr heavily, but just yesterday she asked if I was ticklish and told me that being tickled feels good if the boy is cute, and she also told me she'll bite me if I tickle her, which might be flirting.