Help please

My 2 and a half year old daughter beats up on her 1 year old brother CONSTANTLY while he’s just sitting there minding his own business. I put her on a brief time out every time she does it, and she HATES time out and cries the whole time, but as soon as she’s off, she’s hitting or pushing him over again within 10 minutes. I am LOSING IT. How can I make her stop?