11 year old,constant bickering, WDYD?

[Bubble2bubble]

Dd1 is 11.5 and I know underneath a nice, caring child, but her new occupation is picking on her 9 year old sister.
Dd2 is not in anyway a drama queen and is probably the more socially astute of the two, so can brush it off for a while, but it is starting to get her down.
If I speak to Dd1 it degenerates into "you blame me for everything", high drama, door slamming and and usually tears :(
Is there any solution?

Time and growing up. I shouted and screeched a lot which didn't help.

Not much use, sorry!

I screeched tonight . So ashamed of myself, but feeling like crap with a horrible virus, and just so sick of it.

When my older one picks on the others I do use that classic 'think about how that makes her feel'

No solution but just tell her not to be such a self centred, whinging, malcontent. Take her phone away if she continues to moan. .