Girls who like to make their bf�s jealous...WHY?

My best is in love with his new gf but she does a lot of stuff with other guys that I think is subtly disrespectful, things that are in that gray area ya know, but still questionable.. what I find odd is, is that his girl will do something then ask "are you jealous?" or "did I make you mad when I did that?" and he always laughs and says no... but by her asking those questions she knows what shes doing and hes really in love with her so why would she do that? Its none of my business honestly, but because we go out alot its irritating ya know, I want to tell her to grow up.. what do you guys think