Wanna see?

So, today, I'm a bit confused. I'd gone to a party to see if I could get out of the doldrums I had been feeling lately. I was talking to a young woman in her early twenties. She had just gotten the surprise of her life when her boy friend, a marine, had come back home prior to being deployed to Afghanistan.

I won't share most of the conversation, but at some point, we came across the topic of losing weight. She proudly proclaimed she had dropped forty pounds to a weight under 110lbs. I made some comment about my surprise that she had lost that much weight.

Her next comment was, "Wanna see?" She then lifted up her shirt and flashed me. Her boyfriend was twenty feet away talking to one of my friends. I had just met her for the first time about an hour ago. And she was sober.

I congratulated her and let myself get called away by my friend. About half an hour later, I had to leave, and to be honest, I felt a great amount of relief that her boyfriend missed her little show.

Now, I'm trying to figure out what I did or said right for future reference. Or discover if some aspect of my demeanor causes women that I'm not interested in to feel so comfortable with me. And, of course, how not to get killed by gun toting marines.