K.I.
K.,
See, the thing is, this woman IS part of the family. Just because there was a divorce does not suddenly mean she should disappear. Yes, it was her choice, and not what your boyfriend wanted, but that is the situation. Despite the choices, good or bad, all these people are still her family, too. It might be different if there were no children, or perhaps if their marriage had only lasted a year or two.
I am part of a family in which the matriarch told me, "Once you are part of the X clan, you are ALWAYS part of the X clan." One of the sister's x-husband still was invited (and attended) Thanksgiving, Christmas, cookouts, etc. In fact, I am no longer with the person (long story), but still very much part of the family.
I hope you and your boyfriend can find peace, and understand that this woman needs love and family support, too. I wish you all the best, and encourage you with your lovely family.
K.