Well, she married the guy. Some guys are just like that. I have a friend who I know that if I said something like that to his girlfriend, he'd probably hit me in the face next chance he got, and I also have friends who would think it was hilarious and encourage it. But when it comes down to it, you have to respect his boundaries or you will probably lose both of their friendship. It isn't that hard to watch what you say, and I'll be honest, I don't know how comfortable I'd be with my significant other texting another straight guy and flirting like that. Anyways, you're probably going to have to stop it, it makes your friend (matt) uncomfortable, and if he really is your friend, you should respect that it makes him uncomfortable, and stop flirting with her. Not to say you should cut off contact with her, just watch what you say to her, she is married and some things are not appropriate.