I am pulling away and standing up to DM a lot more in recent years - I think I am getting a backbone and some self-esteem, that I can have valid opinions and am doing pretty ok in my life despite her. (I am physically distant, which does help).
But she has had heart troubles, has IBS and diverticulitis, and recently (last 2 years) was dx'd with diabetes. She changed heart dr as "he told me to eat less, lose weight and exercise" as her main treatment - she wanted someone more sympathetic and willing to just prescribe her some pills but say there was something wrong she could get sympathy for! IBS and diverticulitis kick in anytime anyone challenges her on anything difficult, call her on her nasty behaviours, or she feels overwhelmed and undervalued in life (like if she invites us all to the house, but then she feels ignored at all - she will huff off to her room and be "indisposed" for hours while we all tiptoe around her!). We are getting less willing to do the tip-toeing though, and once we give her a cup of tea to "hope she feels ok soon", we all get on with what we want to do, organise meals to suit regular lives and timetables, and head out to do things as a group of adult siblings rather than scared kids to be dictated to. Admittedly, she is eating a bit better because of the diabetes, but will still scoff a half box of chocs in a sitting without even realising it (and will then blame US for eating all of our dear DSis's chocs - even DSis who got them is raising eyebrows as she knows we all had one each while DM kept eating and asking for box back at her end of the table).
Yesterday, I got a phonecall as DM and DSis drove to my city to go to an extended family event near me. "Did I want to participate in a joint birthday present for DAunt's significant birthday (that they missed 4 months ago!) - we bought her X already, and did I have a card they could sign from us all as well?" (they'd forgotten to get that and no option on Sunday morning to get en route). Well, I said no, I had already bought and given DAunt a present at the time (I was at the family celebration - they weren't, I don't know why), and I also told DSis that if she DID want to organise joint presents, that was fine but she needed to get agreement on them BEFORE purchasing, on the present and the budget, and not give the rest of us a fait accompli. And that I would find some kind of card (most of mine are very colourful and cheerful, not appropriate in this case - I had 1 that just about worked).
The same DSis is trying to persuade us all to go in with her on a picture for DDad birthday or DParents anniversary, that she bought last New Years to go with another we had just given for their anniversary a few days before. I don't like it, wasn't involved in choosing the original but knew that and was ok with them choosing as I had agreed to go in on it and couldn't be there to choose - but I really don't want to get a second one. DSis is just trying to be "the peacemaker, the person holding the family together" in a very PA way, and not actually by bringing people together but dictating what we will all do. (And she is not the eldest, just the one who is single and has recently moved back home, and thinks she knows best for us all but is quite bitchy talking to us about other family members, and very demanding of our time, money and energy - without acknowledging that the rest of us have other committments - and always gives out about not hearing from us but it's up to us to contact her as she is always out with friends and never returns any calls or emails).
Sorry, this turned into a cathartic rant but I am pulling away from them. I have rented a house near them for Christmas this year, so that I have personal space but we still do the family gathering. And I am learning to stand up for myself - but I am always ready for both DM and that particular DSis to turn on me (as both have done in the past and I expect it to happen again soon).
Last week, in fact, I had to say to that DSis that the house we're renting is tiny - she was expecting to stay in it over Christmas (when she lives at home - she thought it would be too crowded with other siblings home), offering to stay on the couch (which is tiny and she doesn't get up in the mornings so we'd have no use of the kitchen/sitting room when DD is a VERY early riser) and also offered DMum the use of the kitchen in MY rented house to prepare for their anniversary party without even asking me.
I have already told her that there is no space - but now that I know the au pair will not be staying in the 2nd twin bed, I will have to be brutally frank with her to say no one is staying. And that I am not having it over-run the whole time - we have to see both my AND DH's families, and I have had too hard a year so really, really need some time out and headspace to unwind - or I am afraid I really will have a nervous breakdown (I have started to unwind a little this weekend, but over the past 3 weeks, I have cried at work 7 times from pure stress - I can't keep that up). So I am not having anyone apart from DH, DD and I staying in it.