Help with new puppy please

My 4 year old granddaughter, loves animals of every description and has always been very empathetic towards them. She is especially fond of dogs, so following some advice about what breed to get, I bought her a Bichon Frise,  whom she has named George. However, her reaction to him has been the opposite of what we expected. She’s heavy handed with him, won’t let him sleep and has even hurt him on a couple of occasions. We have explained to her that he is only a baby and that she needs to be gentle with him and let him have his rest, but this just isn’t sinking in. 

She cannot tell us how she is feeling and has had to deal with a house move recently. Could George have become her outlet for showing us how she is feeling?  Can anyone suggest some strategies to cope with this situation?  On the whole she loves him and plays with him nicely, but her mood/behaviour can turn on a dime, with no warning whatsoever. 

Any help would e gratefully received.