Why do you think she did this?

Pl sp this girl i liked invited me to hang out wwith her i agree.But when i wentt over her friends house whom is a guy, she was itting on another guys lap.When she knew i liked her.Now i'm thiinking about just ******* her and leave.I'm also talking t0 two other females. I wass going to settle down for her, but now i say **** it.