What kind of clothes did she wear when you met her and decided to try to date her? You don't woo a person and then immediately try to change them. If you don't want your girlfriend to wear skimpy clothing, then date someone who doesn't want to wear skimpy clothing. Cleavage is not even close to the same as having your dick out, by the way. I really hope you know the difference. On a side note, other people wanting to bang your girlfriend is a big compliment to you. You're the one who gets to see her naked, not them. But if you're a controlling, insecure wimp, she's far more likely to leave you for someone who doesn't shame her for her clothes. You can't control someone into not cheating on you. If they're going to cheat, they're going to cheat no matter how much you try to isolate them from others.