The situation:
friend A has second home. Friend B has come to stay. Friend B has two young kids aged 2-5.
friends A’s bedroom has a super king. The other room is the spare room but only has a small double.
friend A’s new bf is coming to stay.
YANBU: friend A should gives up her bedroom and stays with new boyfriend in spare room on small double so friend B can be more comfortable with two young kids in super king.
YABU: friend B is ultimately the guest and should be in spare room with her two kids when boyfriend comes regardless as she’s the guest. Even though it’s Friend B’s second home it’s still her bedroom and she should always go there.
friend A and B have been closer for almost 20 years.