Sounds like you are co-dependant, and she is taking advantage of yanking your feelings along all while (being honest about it,) telling you she IS going to cheat.
That is all poly-amorous means is she wants a green light to cheat.
You can't let go and move on when she keeps knocking on your door and you keep sleeping with her. Even though you said no to the poly-amorous you are giving her what she wants. You say no she comes over you two face then she goes and does it with others anyway.
You need to cut her out and go 100% no contact or else she will keep giving you more of the same and you will never heal
