I would say its a bit of both, she is feeling left out, its hard when a new sibling comes along, she feels usurped , it will get better but I suggest some one to one time with you or Dad, take it in turn to play games, take just her out. When you are changing baby, feeding or playing make sure she is part of it.,make sure she holds him under supervision .As time goes on and he gets older and more playable she will feel happier, meantime focus on her positive side and praise her when you see her doing something right ..good Luck