<human>: Can you succinctly summarize the text in 1-3 sentences?

We have been together for 2.5 years, and have a house together. I agreed to have a threesome with my SO, as I like to try new things. One of my requests at the time was that I didn't ever have to see her again if I felt uncomfortable. 

We met a friend of a friend, and we seduced her over the course of a month or so. We had 2 threesomes (as we were very drunk the first time). During that time, my SO became very good friends with the other woman.

I said I didn't want to continue having sex with her, so we moved to a platonic friendship. She now comes over to our house a lot, and we hang out. When she is around, I feel like an outsider. She is very close with my SO, very attractive and funny/intelligent. 

She occasionally does small things which annoy me (e.g. she sits next to him, they have in-jokes and she invited herself to one of his work things), but neither of them have done anything obviously inappropriate. When we are out or at parties, they tend to stick together and chat in the corner together. 

He says he loves me, which I believe. He says he doesn't see her that way any more, which I believe less. He doesn't have many friends, so I don't want to stop him seeing her, but at the moment it feels like she's an extra person in my relationship, and she's doing much better than me.

I've spoken to him about it a bit, but I never feel like I have a proper resolution and I still resent her presence in my home. 

What should I do? Accept their relationship & get over it? Break up with him so he can be happy with her? Ban her from my house?? (I don't want to do that)
<bot>: Threesome gets predictably complicated. How do I reconcile my jealousy and wanting my SO to be happy with his new friend?