It may sometimes be a test to see if the guy can take her or just an involuntary reaction when getting close with a guy.
Girl: Yeah, sounds good. Did I tell you that my dad was a drug dealer who got arrested for beating his crack hoe?
Guy: Umm, no.
Girl: Well, he did. True story. Oh wow, I'm feeling so fat.
Guy: You're like five pounds..
Girl: Noo, I'm fat. I don't think I'm gunna eat tomorrow. I need to get rid of all this jiggle! Wanna touch it?
Guy: There's no jiggle. You're nuts.
Girl: Shut up. Hey, I wanna be exclusive. Do you?
Guy: We've only known each other a week.
Girl: Oh, okay, I see how it is.
Girl: Dammit, I spewed crazysauce all over him!