My [25m] sisters [33f] and [48f] hate each other.

My sisters A 33f and B 48f have always hated each other. There’s been years of ups and downs but things have lately been progressing towards them both completely shutting each other out completely. And for context, there’s 6 of us total and we are all extremely close with the exception of these two sisters which is why we’re eager for some sort of resolution or understanding between the two.

I will try to provide as many details as possible in order to paint a clear picture. Basically, A is selfish and B can be cold hearted so they don’t get along but the rest of us just look past everything because it’s not a big deal. A is not very good with her money and so she has a history of missing birthday presents/ doesn’t contribute as much for family gatherings and what not. She also gets really bad FOMO(fear of missing out) and takes any missed invite as an attack against her. B had a rough upbringing due to our family dynamic when she was born(we are Asian so the fallout of a war led her to be raised by extended family for a few years). Because of that, she has a bit of a different mentality than the rest of us and can be construed as cold hearted at times. She constantly has a guard up and keeps track of everything so she feels slighted whenever A doesn’t send a gift or isn’t contributing as much as everyone else. The rest of us don’t care, we are family and are able to comfortably make ends meet so if we have to contribute more for someone who isn’t able to, it’s not a big deal but B does not like it when A isn’t able to contribute equally. And for context, B has struggled financially in the past but the last few years have been really good to her to where she can live a pretty luxurious life. B can be really generous with her money but since she keeps track of what everyone gets her, she doesn’t ever get A anything or takes her out to dinner like she does with the rest of the siblings. Again, they are in completely different financial situations but B was struggling when she was A’s age so we try to tell her to be more understanding.

Everything is kind of coming to a head because A is having a destination wedding next year. Her thinking is that, since the venue is cheap and less people will want to travel to make the wedding, the wedding will be cheaper for her and her fiancé. B is not happy with this at all because she is apprehensive about the location of the wedding and is constantly complaining about the price. She is very vocal about her apprehension but she also spends pretty wildly on luxury goods like designer things or nice brand name things, and has 6 figure luxury vehicles. So, A is getting upset that B is being vocal about her concerns when she spends so much on other things but is complaining about her sisters wedding. Also, B had A in her wedding party when B got married. So now A doesn’t even want to have bridesmaids because she feels obligated to have B on her wedding party but their relationship is the worst it’s ever been which the rest of us feel sad about because we want our sister to have a nice carefree wedding without all this stuff looming around the family. A also takes any of the other siblings cordialness with B as us taking sides against A. For instance, it was recently A’s birthday as well as a different siblings significant other’s birthday a day later. B only took the other sibling and their family out for that siblings significant others birthday but didn’t offer to take A because of their relationship. So in turn, A is upset with that sibling and thinking that B is conspiring to get everyone against her using her money and talking bad about her. Myself and my siblings think both are being ridiculous and petty and upset they are 1. Talking bad about one another constantly and 2. Being immature about everything rather than working on mending their relationship. We are stressed out from the constant fighting and bad mouthing to get us on their side but none of us want to take sides which puts us in a worse position because we call them out when they try to bad mouth the other. I guess I am asking for advice on how to mend this relationship or asking what you guys think they need or if there even is a fix to this. I have left out a bunch of their history that would explain things but wanted to just keep recent pertinent events for now to give context but feel free to ask any questions.

Tldr: sisters hate each other so much that one doesn’t want to have any bridesmaids at her own wedding because of the obligation of asking the sister she hates to be a bridesmaid