what to do in a situation like this??

last weekend, I had a party at my mom's friends house, their daughter who is really pretty and she is my homies cusin. well we are pretty close and so we were like chating and chilling in her room and we were having fun, until some dude stepped in, and after that she does not talk to me anymore and start to talk to that dude, I dont understand, is she trying to make me jealous? or she just dont give a damn about me? cuz we are pretty close and I think she likes me and I like her too. so anyone know what should I do in a situation like this?
appriciate any help

Maybe it's not about you. It's about her and the fact that she wants that other guy, and you just happened to be there. Don't get all twisted up about it- she is not your girlfriend.

it was only one night. nothing special happened. and if you were really close to her and knew her as well as you portray then you must've know that she either had a boyfriend or something like that. but other than that, i agree, dont freak out. just give it some time

Maybe she was just talking to you? How come everyone thinks that when a girl talks to them they always want them?...wait, what the ****...im like that too!