Deliberately trying to be vague/neutral so I can sense check this without all the backstory.
Fairly new couple, X & Y have plans to spend NYE together at one of their homes. Both are very busy so they see each other around once or twice a month usually. X has developed a moderate cold so Y cancelled the plans. X is annoyed because Y is getting over a cold anyway and upset because they will be spending NYE alone. Y doesn’t want to risk catching another cold because they’ve already had a couple over the last month.
Who, if anyone, is BU?