What should i do if my daughter saw some other children playing and she snatched away their ball?
You have not mentioned Maggie’s age. However, there are 2 issues here. Linda and Peter’s bullying of Maggie and Maggie’s reaction of taking away their ball. You may find that Linda and Peter will treat Maggie with more respect if they get to know her better. Invite them over for a game or go out and play with them on the street. Maggie and the other children need you to be the peacemaker/arbitrator. It may be beneficial for you to inform Linda and Peter, in subtle way, that Maggie is different and that she may act or react differently to them at certain times. Help them to build a relationship with each other. This might start with Maggie returning their ball and saying sorry.