<human>: Can you summarize the given text in a few sentences?

My aunt and uncle live in the same town as my grandmother and always bring her up to my mom and dad's house (2 hour drive, grandma is the mother of my dad and aunt) for Christmas. It has been this way for years and years and years. This year, however, my aunt informed my mom that Aunt and Uncle are NOT coming for Christmas, having instead planned themselves a trip elsewhere to which no one else is invited.

My mom is super pissed that they are 'abandoning the family' for Christmas, but was somewhat mollified by the belief that Aunt and Uncle will be taking 91 year old grandma on the trip with them. I was hearing drama from my mom about how my aunt is being rude and drama from my aunt about how she can do whatever she wants for Christmas and it isn't fair that my mom is bitching her out, and I was kind of tuning both of them out.

HOWEVER. A new dimension has emerged. My aunt is NOT actually bringing my grandma on her Christmas trip. Instead, she is going to watch an 'old Christmas movie' with her on Christmas eve, have breakfast with her in the morning, and then leave Grandma alone at her assisted living facility for the rest of Christmas. She refuses to tell my mom Grandma's actual Christmas whereabouts because she doesn't want to 'deal with the criticism.' 

So, dilemma. My mom will be pissed AF if she finds out that Grandma was all alone on what may be her last Christmas (she's not in great health), and especially so if she finds out I knew and did nothing. My husband volunteered to drive out and collect Grandma and bring her to my parents, but if we do this, my aunt will be revealed as a Grandma leaver-behinder and my mom will freak out that she was lied to by omission, and cause even more hurt feelings between the two of them, plus my aunt may be pissed at me for outing her. My aunt claims Grandma "would rather stay home" but since usually Grandma hates to be left out, I find it hard to believe. I haven't called Grandma herself about it yet.
<bot>: If I do nothing, my grandma will be all alone on Christmas. If I go and fetch her, then aunt vs mom drama will intensify. What to do?