Hello how frustrating this can be for you. I think if things escalate you may need to take her to the emergency room. She needs to be medicated, as you know. I would not worry about the other woman because her pattern is to break up with them after the mania is over. If she does not agree to go to the hospital all you can do is wait until she is ready to go. When she is not manic any longer have a long conversation with her about her behavior when she is manic. Tell her then how much this behavior hurts you and how you will not tolerate that again. I know this is an emergency situation and I am glad you are conducting her family. Do you think someone can come over to the UK and talk some sense into her. Do not argue with her tell her that you will let her do what she wants to do see the other girl, but ask her to see the doctor and take her medication. I can't help but to believe that you deserve better than the treatment she is giving you. I also wonder how is your support system? Do you have friends who can offer support? How about an intervention with family and friends? You can schedule one when everyone who loves her can be there.