Why she accept the situation which i hated...?

i am a bi-woman. my ex whom i am living till now though we don't have commitment had a new found girl. they had been for barely 3 months. i knew her when we had a city tour together with my ex. i blew my identity to her which enraged my ex but despite of that, my ex chooses to stay with me. she explained to the new girl that my ex can't leave me coz of her commitment with me and that we will always be together no matter what happens. i was totally awed how this new girl accept the situation that her current love is staying with her ex and it's just fine with her. they are chatting and talking over the phone everyday and my ex visited her when she is free from hospital shift duty. it hurts me whenever my ex is out of the house and i knew where to whom she is with. i talked to my ex that we have to part ways and my ex told me it was my request but never will be her decision. i am disillusion coz i can't go living in this hell like situation while the new girl can easily adjust to the situation. does she really loves my ex that she can stay suffering thinking what we are doing the whole 24 hours; she loves her too much that she understood my ex commitments and responsibilities. she told my ex that she had choices, to stay out of the situation or stay put and she chooses later coz she is in love. i need and honest to goodness advice. i am falling deep down the drain. please help. thanks.