Is this messed up or what?

So I was talking to this buddy of mine then I told him about this girl I was hanging out with. He encouraged me to go for it and try to date her. But today she tells me he is asking her out to dinner and stuff, should I be pissed that this guy is trying to 'poach' this girl or is this a fair game for him to be going after her when I told him I was hanging out with her?