This is a complicated story, apologies in advance and many thanks to those who make it to the end!
This is about a situation my mom is mostly in, and I wish I knew how to help her through it. She is a mother of three, has been widowed for 11 years, and has not had it easy in life. Several years ago she got her real estate license and has been doing really well with that. Not rich, but enough to pay her rent, and a huge improvement from the high school cafeteria she worked in. A few years ago, my mom's brother on the other side of the country asked for her help finding them a home out of state. Long story short, she could have received a referral fee for her work, but they decided at the last minute they needed a home with a pool and cut her out of it. My mom was hurt, they don't talk anymore, and the rest of her family was upset about it too, but things faded away and everyone moved on. (My mom has helped a lot of other friends and family find new homes and there haven't been problems)
But last year my mom's sister, who lives nearby and who she has always been close to, decided that her family was ready to move to a new home. My mom spent time over the course of the year showing them homes (at one point she was even drawing up a contract, but they changed their minds on that home), then suddenly she stopped hearing from them. Not just about their home search, but just the general conversations they used to have - my aunt even stopped inviting my mom to all of her young children's school plays and sporting events that my mom would always go to. Finally, she heard that they had found a monster of a home (almost a million dollars, a lot bigger than they had been looking at before) and that my aunt's husband had decided to get his real estate license in order to save them money. My mom was crushed, and not just because of the money. They didn't even tell her to her face, she heard it through other relatives. My mom is so nice, and didn't want to sound petty, so never confronted them, even though the bigger issue was about her feelings, not the money.
I was out of the country most of the year, and one day was so tired of hearing about how sad the situation was making my mom. I'm not as nice as her, I have no patience, I already had a raging malaria fever, and I blew up. I sent my aunt a message online saying how disgusted I was with what she had done, how she had taken advantage of my mom's livelihood, etc. It wasn't nice, and if it was going to be said it should have come from my mom, I know! I had been so frustrated seeing my mom do so much for her family with so little, and them taking advantage of her because she is older, single, and not well-off financially. The situation just blew up from there. Her response to me was "I love my sister, your dad was an asshole, grow up" (I am a married adult btw). She then stormed into my mom's house, hovered over her and screamed in her face about how she doesn't like my mom's personality, attacked my younger brother's personality (he is a kid and was in the house), and said a lot of other terrible things that didn't relate to their new house. She did admit she questioned her husband's decision to get his license at first, but then couldn't say no to the savings... (ironically they overpaid for the home in the end, some savings

She also mentioned that their company made $4 million this year, irrelevant other than to make my mom feel small, while also proving how much they didn't need the money my mom would have received.
My aunt and her husband then continued to send my mom and I messages about how petty we are, how much money they make, etc. etc. One message said "you've attacked my family, this is war, expect retaliation." Yeah... I only responded once. I sent an apology for lashing out at her in my first message, but reiterated more calmly that from my perspective, what she did was wrong. I said I really just wanted her to know how much my mom had been hurting for a while now, and if she really loved her sister she should at least try to sit down and let everything be aired in a more humane way. That was the last I heard from her. I feel terrible for sending that message in the first place because it was a catalyst for this huge fallout, but at the same time, my mom says she is at least glad to know her sister's real feelings for my family. I'm not sure that those are her true feelings and weren't just said out of anger, but my aunt has too much pride to ever apologize for anything she does. Meanwhile, I feel so guilty about this that I'm apologizing to my mom all the time!
I'm posting this now because I spoke to my mom today, and she found out through my grandparents that my aunt is having all of the relatives over to their new mansion for Christmas, so of course my mom is not invited. I don't even think my mom would go, but I just can't imagine doing that to my siblings, especially knowing that they had no one else to spend Christmas with. It also makes me frustrated because I have no idea what my aunt may have told everyone about my mom, and she's a great person! Not being with them this holiday is the obvious choice since it's at their house, but what about future holidays hosted at someone else's home? My mom doesn't want to speak with her sister, but she also isn't willing to let it all go- she still misses her nieces and nephews at the very least and is still so irritated by the whole thing. What have some of you done with bad family situations? Did you reach a point when you knew it was time to let them go, and how did you know it was time?
It has also just been really sad/strange/frustrating to see my aunt change over the last few years. She is significantly younger than my mom, and her family had a hard time getting started after they got married. My mom spent whatever she could to bring them groceries, she cleaned the house and cooked when they had babies, she watched the kids any time they were in a bind. But then my aunt's in-laws decided to buy them a house and give them their company, and they've never been the same since. She acts entitled and sticks her nose up at things that were the norm for her just ten years ago. Even tomorrow, my mom will be at the hospital all day waiting for my grandmother to get out of surgery, because my aunt already had tickets to a Christmas party at some fancy lodge that she just couldn't fathom passing up. She's a completely different person, and I don't want my mom to waste her energy thinking about this situation anymore. I guess that's all. Thanks for letting me get it all out!
Re: Relationship with extended family falling apart- what would you do?
Your mom has to figure out what she is hoping for, will the extended family believe the trash talk, will your grandparents defend her? If I was her I would make the best Christmas for my kids and be done with it.
Also you need to stay out of it, this is between the two sisters and although you have your moms best interests at heart you are making it worse.
This is how we handled holidays we weren't included in, my dad was divorced, some of his family had a religious conversion which made them ultra religious and anti divorce, after this holidays evolved into them and us for a few years, the majority of family members chose them because at first they didn't know my dad and by extension us, had been ostracized, and they had the big house, lots of $$$ etc.
We just started our own traditions, my moms niece had always joined us and continued to do so, eventually some of dads family drifted back. It was hard on my dad, he came from a really big family but he refused to compete for them.
You're painting your mom as being the victim here but the same thing happens with BOTH of her siblings? Maybe they are both assholes who are the total wrong-doers here, but usually that's not the whole picture.
As for the holidays, who is "all of the relatives"? My advice is for your mom to extend an invitation to whoever she wants and either have them over Christmas Eve or at another time during the day on Christmas itself. As at least a couple of these people are her parents, I would assume/hope they'd want to come and spend time w/ their other daughter.