My dd is going to be two next month and I'm really struggling to get her to understand sharing. We had two other children the same age round for lunch today and my dd was a nightmare. Every time one of the other children picked up a toy or a book she would charge over and shout at them and snatch the toy. I don't like to take the toy physically from her as that feels like I am teaching her that snatching is ok. I try to be calm and ask her to give the toy back but she wails at me and refuses to give it up. I feel like I'm letting her down. I don't want her to become the kid who the other parents and children dread seeing 
Can anyone give me some hints or tips on how I can deal with this?