Sister has inherited huge wealth. Help

I hope she gives some to you and your parents. Assuming you have a decent relationship with her. If she really does just waste it all then I'm not surprised if you disapprove.

I'd have to say something, probably because I couldn't imagine being like her in similar circumstances in a million years!

Maybe put it to her that it would be nice for Mum and Dad to have a little comfort now since they brought you up and made sacrifices. It may trickle down. If she is blind to your family's circumstances and does not make a contribution I'm afraid I would have to cut ties. You could not tolerate being around that level of blindness to other's circumstances, particularly when she actually TOLD you of her good fortune.

Anyway, what goes around comes around.

She sounds pretty awful tbh. You can come into serious money, and you can also be tactful about it. Money used to whisper, these days it seems it screams it's bloody head off.

If the rest of the family are struggling and she's spraying up to £300k a day, I'd wonder what I'd got in common with her anymore.

I'd wait for a while and see if there was any money forthcoming to the various members of your family without her being asked, and if there isn't I'd be calling it a day in terms of a relationship. It would be a deal breaker for me. To come into multi millions and not want to help out family is selfish in the extreme.

Just tell her. You’re struggling to make ends meet and it’s stressful and she is bragging about a load of expensive crap she has bought. It’s fine if she doesn’t want to share but you and your parents are struggling so it’s hard to get excited about her new xyz

You say the circumstances are sad so therefore maybe I wouldn't envy her.

I voted YABU because I don’t think it’s possible to explain nicely. It won’t work. But YANBU for feeling the way that you do

She’s being a dick, you don’t have to be happy for her.
If she had an ounce of sensitivity you wouldn’t know she was spend spend spending because she wouldn’t be rubbing your nose in it. Quite apart from the fact that some people would choose to help out the struggling sibling in this situation.
While you aren’t entitled to any of her money (not that you have implied you think you are) you are entitled to some consideration over the difference in your circumstances.

She sounds terribly selfish. I cannot fathom anyone who could spaff money up a wall while their immediate family is struggling. Her money, her choices but you don’t have to stand there and applaud her.

What did she spend 300k on?!

Telling her how you feel may be interpreted as jealousy and not being happy for her. Would it be better coming from your parents to gently tell her it’s a bit crass going on about her spending?

Ask her to give you some money.

"Reign it in, love." might be the only thing you can say, both for spending and telling you about it, as she's not being very tactful.

Not a lot you can do, I'd swerve her until she's spent it all.