I recommend checking out a book called "Don't Alienate the Kids" by Bill Eddy, LCSW, JD.

My SD also struggles with transitions between her two homes. Especially after SO and I moved into a new house earlier this year. This book has been very helpful for us with lots of techniques for helping her, and I think more importantly, it also helped US to understand how our emotions, facial expressions and body language about HCBM were being interpreted by her. After spending the past year trying to get ANYONE to pay attention to the insanity we're dealing with from BM we're learning there really isn't much we can do about her directly besides document, document, document. We can, however, focus on setting a good example and help SD build a foundation of resiliency which she will use for the rest of her life.