This post has the potential to be a hot one, so I wish all "peace" and please be kind to me, too...I do want opinions from all sides of the triad though.

My adaughter was born to my stepdaughter, some of you may remember, and I'll call her, the bmom, J. J has lived with S, for several years (he is not the bdad of my daughter) and they have a son together, whom I'll call C. S also has a little girl from a former marriage, whom he sees on a not-too-frequent basis. They have just moved to our small town. J really doesn't show any particular interest in K, my daughter, which is fine, but sometimes HER mother, the bgrandmom, will start up some sort of thing to entice K over. She likes to pretend that my husband (her exhusband) and I didn't adopt this child and so she just creates this other "reality" and goes along telling friends and distant relatives," Oh, and this is K, J's daughter..." as if she is parenting her and we don't exist. As K puts it, "Here we go again. Time for the C and K are both J's kids show again". I have recently put a stop to all contact with bgrandmom with the exception of family gatherings where my husband and I are also present (birthday parties for the grandchildren...in addition to C, there are 2 other grands from another stepdaughter). K just keeps her distance from bgrandmom.
Here's the current drama: In the new house they are renting, J and S have a "bedroom" which their son, S (who is about to be 5) proudly told me belongs to his SISTERS, ___ and K! (The half sister he has from his dad's first marriage and MY DAUGHTER). We went thru a round of several therapists years ago who were adamant that K refer to J as her SISTER, which legally she is (her half-sister, as they now legally have the same father). J is her bmom, but K absolutely DOES NOT want ANY of us referring to her as such and especially does not want the grandkids to be told that J is her bmom. J has pictures of "their 3 kids, ___,C and K" in the foyer, as if they parent all 3. K has not spent a night with her in more than a decade and the idea that there needs to be a BEDROOM for her is ridiculous! Furthermore, it would create in K's mind (I have not allowed her over there yet, she doesn't particuliarly want to go, and doesn't know of the pictures/bedroom, etc.) an expectation that she is supposed to spend time there and pretend to be J's daughter. J is having a birthday party for her son soon and expects that we will all be there. We will not be taking K, as I have made plans for her to spend the weekend with a family member out of town to avoid alll this. We will be there because this little boy is our grandson and we love him. We also love J, but I am very angry over the all this. WE made it clear a few years ago that upon the advise of the therapists, she and her mother (bgrandmom) would observe the fact that she is K's sister and enjoy that relationship with her or she could have no relationship at all. Under the circumstances, it would not be possible for us to have it any other way and have an emotionally healthy environment for K and ourselves. J and her mother have been telling C that K is his sister, not his aunt. For that matter, they were telling the other grands that, but they are tiny and I think that has stopped per the other stepdaughter. So this is their way of circumventing the groundrules. This HURTS my daughter!!! A family member suggested K be the one to tell them how much she is hurt. I asked what she thought of that and she said, "I think that is wrong because I am 11 and I am a child. Children shouldn't have to be the ones to say this stuff". I agree. What do you guys think? Sorry for the ranting and the length. Thank you so much.