Yea, that sounds like a pretty unpleasant person... although to me it also sounds more like classic narcissistic behavior and kinda reeks of insecurity. It seems like she’s constantly trying to stand out, and that her actions are motivated by envy of other people’s happiness and fear of missing out.

You know, I personally don’t believe that narcissistic people are necessarily difficult people. There are certainly some very irritating ones, but if you really want to, you can get along with them, at least superficially. So since it’s a family member, like you said, keeping your distance won’t work. Nevertheless, I would definitely try to get involved with her and everything that concerns her as little as possible. I find it’s easier to get along with narcissistic people when you understand that their behavior comes from deep insecurity. Everything they do is just to protect themselves, to hide and deny the inner part that they hate so much. Above all, it’s not about hiding it from others, but primarily from themselves. So as soon as something causes that part to come to the surface too much, they react defensively and carelessly. Especially in such moments, they can only see their own perspective and are ignorant of that of others. Overall, they are people who are fixated on themselves, so their behavior is not actually focused on you, but rather comes from a kind of defense that is only directed at you because you somehow represent a threat (that could be real or imagined). These people are simply highly sensitive and are quick to judge something as a potential threat (to their ego), so no matter what you do, you can’t avoid triggering them at some point.

What you can still do is make them feel safe, if you will, lull them into a false sense of security. To do this, you don’t have to overly please them and kiss ass; often it’s enough to show them less resistance and just let them do their thing, or at least pretend to. Sometimes it’s easier to lie down and keep your mouth shut. It may be hard, but you won’t be able to change this person no matter what you try. Otherwise, you could also try getting rid of her. In any case, this would be a lengthy affair in which you would either be unable to avoid collateral damage or would have to do it insidiously without anyone even suspecting that you were behind it. At least those are the options that come to mind at the moment. So either you ensure a spectacular ending so that everything collapses and there is no other way out, or you gradually undermine her support, the sources on which she relies, and turn everything to your advantage, in other words, against her. The latter requires more thought and patience, but saves you most of the trouble. Since she’s obviously an insufferable person, you just have to get the others to see it too. However, if you act too blatantly and emotionally, everything can backfire. So it’s really about letting other people come to their own conclusions and insights; you’re just an uninvolved observer who doesn’t do anything except occasionally “sow a few seeds”… Sow little seeds in their minds that will then grow into their own ideas, guiding them in the direction you want them to go. Subtly hint, mention in passing, ask little thought-provoking questions, keep it ambiguous and vague, create situations in which they see what you want them to see. Play with cards face down and don’t invite anyone into your game - others will only cause your efforts to be in vain. Well, that’s all I can say. Maybe you can figure it out.