#3 Spend more time with her. If you want to have $ex with a girl, the only time you can work your magic is by getting some alone time with her. You need to flirt and make her feel comfortable to be with you. But you can’t do that when there are other friends around.
Behave normally when there are other friends with her, but the second they walk away, say something like, “whew… now I get to spend some alone time with this nice girl…” or something else that makes it clear that you find her attractive in a more-than-just-friends kind of way.