It would piss me off too. So, you're not alone. It would bother many, many other guys as well. I think it's a tendancy to be the Alpha male for our lady, we know that when a guy talks to a girls, most of the time, he has one thing on his mind, and we don't want any other guy thinking that way about our girl. PLEASE NOTE WHEN I SAY OUR I MEAN THE BOYFRIEND, IN THIS CASE YOU FOR YOUR LADY I think you need to realize that she is her own person. Make it clear that it bothers you, but be nice. Don't be butt head and get all violent, threatening, insulting, etc. that many guys do. That doesn't help. I've heard of things like this happening with guys whodon't know how to deal with things well, and it's criminal, doesn't show love, and shows stupidity. If it bother you and she doesn't do anything different accept messages from the ladies who flirt with you. "What's good for the goose is good for the gander". If the relationship is strong you'll both pull out ok, if not than you're better off without an unfaithfull girlfriend.