9 year old dd developing a nasty side

[Dancergirl]

This is probably perfectly normal but I can't help being upset. My oldest dd who will be 10 in May is developing a side to her that I don't like. For example, she will be rude, impatient and sarcastic - mainly to dd2 (8), sometimes to dd3 (4). She's usually polite to me and dh though.

She and dd2 have always been, and still are in many ways, very close. They'll play together for hours on end and I never need to entertain them. But lately it all seems to be ending in tears with dd2 claiming that dd1 has been 'mean'. And I've heard the way dd1 sometimes talks to her sister. Today they were icing cakes for dd3's party tomorrow. Dd2 had the sprinkles that dd1 was waiting for and I've never heard such sarcasm and impatience from her. Or if dd2 does something by accident, dd1 will over-react and blame her.

How do I handle this? I know it's a difficult time and dd1 is starting to go through puberty and must be full of hormones. But on the other hand I want to get the message across that it's not acceptable.

[MCos]

I have same problem, with DD1 almost 9. She can have a very sharp mouth on her. She still plays for hours with DD2 (7), but can be very sarcastic with her. Has DD2 in tears on a regular basis. She often has attitute and not nice tone in her voice when speaking to me too. I pick her up on it immediately and usually receive an immediate apology.
I am hoping she is a lot nicer to her friends, or she won't have any left!
I'll be watching this thread for ideas too...

[kreecherlivesupstairs]

Dancergirl, you've just described my DD to a tee without the siblings though.
I do think it is puberty and wanting to feel grown up. sometimes she can be the lovliest little girl, other times she is nasty. She is very quick witted and comes out with some hilarious (but nasty) put downs.
I have tried to point out that she won't keep her friends that way, but she doesn't care.
I don't know what to do either, so am now watching for more input.