Well why I would talking about "Shouldn't" feel that way, is because they are selfish feelings, they are jealous feelings and I've always felt that poly people should be able to better deal and address a lot of that stuff.
So after taking what a lot of you folks said into account I talked to her. I told her in no uncertain terms that I was hurt by what she did and how she did it. I explained "hey, even if we're not together we were, and we were big parts of each other lives, you can't erase that for the sake of some guy that just walked into your life"
I asked her about why she couldn't just be up front with this guy, and let relationships happen naturally because it would happen if she wanted a mono relationship with him, I would back of and move in to a support role, that's ok. She basically said the last time she was trying to date a guy and told him about our stuff the guy basically told her she was "a fat attention wanting slut" and a lot of other things. So as broken as girls can sometimes be she assumed all guys would think that of her, even if they didn't state it. She got some similar disparaging comments about her choice in boyfriend from friends and family over the years too.
So we talked a lot, and she talked to this new boy and we talked to him together. She's realizing that if someone truely cares about you and wants to love you, they will do what they can to let you be happy. So we're "back" together for now. The new guy is still dating her and really seems like a nice guy. Might even turn into another guy I can go have a beer with.
It's frustrating though ... having to go through all that to get to someplace I feel it should have started. I hate that guys have to be like that. You know just because it's not your choice doesn't mean you have to be a *** about it. I had no idea some of the stuff she dealt with happened even, she didn't want me to worry about ... or kill the guy that called her the above thing.
Thank you everyone for forcing me to face this rather then being upset and "alone" with it.