My fiance wants to dress more revealing like she used to when we first met, but I can't stand it.. please help

I'm a 22 y/o male. When I first met her, she liked to wear mini skirts and shirts that showed a good amount of her chest. She's a very attractive petitie asian girl, and immediately i was in love. Sometimes guys would check her out when she wears her ier clothes and i noticed that. I became jealous. She has a smaller chest and doesnt always wear bras, and some of her bras just dont fit her tight. Consequently, when she would bend over or move her arm a certain way, I could see her on a few different occasions, when she would wear a low cut top. I expressed my feelings on how upset i get when guys check out her rear, or how hurt i would be if they saw her , or just checked out her . She agreed to stop wearing that stuff. 6 months later I joined the coast guard, and im 500 miles away from her. She now wants to wear her "y" clothing again if she wants. She said if it makes me sad, she will break up with me. It still hurts, but what do I say? I love her.