I'm not sure where to post this but just wondered if anyone has had a similar experience and how they dealt with it.
DD is 2.4 and is fulltime in nursery - she has been there since 11mo and has always loved it, has some lovely friends there, we really like the staff. When she was in the baby room she had a real attachment to a little boy who is about 3 months younger than her - she can be quite bossy and he was quite 'biddable' at that age but they seemed to have a nice relationship, she talked about him lots at home. I have met him mum lots of times, we get along well and always stop to have a chat if we pass at drop-off / pick-up time.
Anyway, when DD turned 2 she moved up to the next room and has settled in really well making some strong bonds with some of the other children and still enjoying it there. 3 months later, this little boy also moved up but he seems to be a completely different character now. He is physically quite big for his age but he's not very verbal yet and my DD is clearly really intimidated and upset by him. He gets very close to her, kind of stands over her and I have seen him hit her, slap her etc with no provocation whatsoever. When he gets close to her (sometimes he kind of corners her) she starts making this awful noise that I have never heard her use before and she gets completely panicked and anxious. I have never seen her like this and it is so so upsetting. The times I have been there and seen this, I have got right down to their level and pulled her out of the situation. I have tried to make eye contact with the little boy and explain to him that she doesn't like it when he gets so close but as he's not as verbal as her I'm not sure if he is understanding me but I get no signal of comprehension from him. When I come in he often comes and takes my hand or grabs my leg and I think this upsets her more as she starts saying 'that's my mummy, not your mummy!' and trying to get him away from me.
I have been trying to have a proper meeting with her key worker to talk about this since it started a few weeks ago but we have kept missing each other. However from the conversations I have had I know that the staff are aware of what is going on. I think he is like this with a lot of the other kids too but more so with my DD - I'm not sure if it's because of her strong reaction to him or because they used to be so close when they were younger and he is just more interested in her. The nursery workers say that they think he is trying to be friendly but he gets upset that she doesn't want to play with him any more and also not being as verbal means that instead he lashes out physically. They try very hard to keep the separate but of course it's difficult in a room of toddlers. I saw him hit her really hard on the face this evening - she was just standing there holding my hand waiting to leave, not doing anything and he lashed out. She was understandably really inconsolable. I have been very clear with her that hitting is completely unacceptable, it's one of the few things I have been incredibly stern about so this must be hugely confusing for her.
I have tried giving her some tactics to deal with him - saying that if he comes up to her and she doesn't want to play with him or he is not being nice she should say NO very loudly and then walk away. The nursery staff are telling her the same thing. She is such a lovely sparky bright little thing and it breaks my heart to see her so cowered by him and I don't know how to equip her to deal with it 
Thank god it was raining this afternoon as I cried all the way home I just feel so sad for her and so powerless.
What else do you think I can do? What do you think I should be asking the nursery staff to do to help? I haven't seen this boy's mum since it all started and in a way I'm really glad because I don't know what to say to her or how she feels about it.
I'd really appreciate some advice. I know I've got to let my DD work out these kinds of things to some extent with me helping her from the sidelines, but I feel she's just so tiny and helpless. It honestly just feels like bullying and I am heartbroken.