Either she still has feelings for you or she wants to be friends.
He is probably just afraid that his exgirlfriend would get jellous and do some thing to his girlfriend, if she found out who his new girlfriend is.
You would flirt with your cousin just the way you would flirt with anyone else.
You flirt with a girl like you would flirt with a guy.
giggles, touchy on the knees/arms/chest(to guys)/shoulders, talking a bit more than usual in a high pitch voice(for girls), fake laughs etc.
you start off first-start to get touchy with him, and he might be touchy back.
You just have fun. If you are a boy...... You just have fun, don't get too touchy, and make the girls laugh. Also compliment them. Also be friendly If you are a girl....... Just be friendly, fun, and nice.
They would flirt with each other throughout the entire party.
All of them.
JoJo
The best thing you could do is ask him directly as he is the only one that can answer this.
No
Miley Cyrus.