How do you deal with competition from other men/women?

Let's say you are out and your bf/gf is hot and people are always starring. Guys can't help but look at my girl, but they don't stare. But let's say you go to the bathroom and someone is hitting on your girl and she is laughing hysterically. How do you handle it? Would it be coming from a point of insecurity to walk up and take her away from the situation? Personnaly I would just walk up and put my arm around her, I don't think it is coming from a place of insecurity to do that, alpha males are territorial by nature. But let's say she is gawking at guy while you are out, or she is holding onto your arm and some guy looks at her and she suddenly lets go. How would you handle that? I would think either confronting her by jokingly saying that they would make a cute couple or giving her a taste of her own medicine is the way to go. A jerk thing to do is to get mad at her and let her know that is not OK and we all know how women feel about jerks...What do you think is the best approach?