A couple of points are really standing out to me, from what you've written:
Originally Posted by Wondering
. . . somewhere something went wrong. I was being cut out of things. He would start leaving the room to talk to her. It felt like she wanted to forget i was there. . . .
She and i dont talk bc she doesn't want to get to know me. She wants to keep the 2 relationships seperate and that isnt what he nor I want. . . .
What you describe is not polyamory, at least not where your husband's Gf is concerned. Poly is the concept of being engaged in multiple and simultaneous loving relationships, based on respect and concern for everyone involved. Your husband's girlfriend is not behaving in a way that shows respect and concern for you. You may have a cowgirl trying to cull the stallion from your herd. You are dead-on right to worry about her. Watch your back, girl!