Can't agree more with AT and Mono. Ignore her. Spend your time with those you like and treat you with respect and ignore the others. Make sure you have some clear boundaries that you don't want to see her, have her at the house or have any part in her life. You never know, in time she will either be less interesting to him and move on; it could be unappealing for him to have her separate from the rest of his life, or, she could come around and reach out to you. It might be an idea to make sure she knows that option can be open in the future if she requests it.
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