My friend had this problem with her 10month old baby believe it or not. She was in bits so sort proffesional hep from a child pcycologist. He advised he to each time her son did it. Tell him 'No hitting or you will go in your cot' (safest place for baby that age). Then if he did it again she was to tell him 'You are going into your cot because you hit Mummy' and put him in there for 5mins. This took about a week to work but the incidents of hitting reduced almost immedietly. Her son would then raise his hand to hit but not do it. The child pcycologist told her to do the same even when her son just raised his hand to hit and that soon stopped too. I would find a safe place to put her and be consistent. 1 warning then 5 mins alone until she calms down. No talking or eye contact and ask her to apologise before giving a big cuddle. Also whenever you notice her playing well, give her ots of praise and attention so she feels rewarded for the right kind of behaviour. Good luck!!