Coping with Difficult Member of family

There are people who are just like the 'Dementors' in the Harry Potter films - they whirl all around and envelope you in a grey cloud of misery, and suck all the happiness out of everything. This lady must have a miserable life - or does she seem to 'enjoy' her moaning and carping?

Good advice, so far, imo.

Another idea - entertain yourself - when you have to see her, beforehand, guess how many negative remarks she'll make or how many times she'll complain about her "hard life" and how someone else is to blame. Then count the number of times she does it and see if you're right. She'll be complaining, criticizing, whining, but you'll be playing a (silent) game and having fun!

keep negative people at a distance they taint everything,we have lifelong friends who always plead poverty and its very wearing ,especially as they are off on holidays every month,drive a top of the range new car and drink like fish.We've stopped seeing very much of them over the last couple of years and life is much pleasanter without all the moaning .

I once knew someone very similar and found it so difficult to cope with her. I did find one small solution. I began to think of her as a "client" - almost pretending that I was her psychiatrist. That way I would always be curious as to why she spoke the way she did, why she put others down, what made her tick. Obviously this was all in my head and I never voiced any of my thoughts. She became somebody I studied, rather than an acquaintance.

Obviously I avoided any unnecessary contact and was able to cope with the times we were flung together. In my more generous moments I could even feel a little sad for her. In my less generous moments she had me tearing my hair out.

Just rant on here! - we will listen!

I would keep contact at an absolute minimum. Yes, you live near each other and yes, her sister is your best friend but it should not be impossible to compartmentalise your social life so that you only meet at family occasions when there are enough other people around to dilute the unpleasantness .
Either that or speak your mind and live with the consequences for a friendship which may not survive, your relationship with your DIL and also your son.
You need a stack of "prior" engagements up your sleeve.