Grief but the person hasnt passed yet, and a complex relationship is present

My friends mum is due to pass on soon and my friend is navigating a complex grief situation where she has experienced significant childhood trauma and has a complex relationship with her mother.

I'm seeking a book that will help her navigate this event. Even any books intended for after someone passes but holds space for the complexity of a difficult relationship with the deceased would be appreciated.

I've found "the pretty painful goodbye book" but I'm concerned that this seems tailored toward a relationship filled with love. Would appreciate insights on if this assumption is wrong though!

thank you