My daughter has a hard time making/keeping friends

[Shayelene]

This may be too long of a story, but my 10 year old has had a friend since they were born. They lived far away and saw each other only twice a month, or so. This girls Father had cancer, so we convinced them to move near so I could help my best friend with the kids/father. My best friends kids started at my daughter's school in 2nd grade. Their Father recently died. However, during this time, my daughter and this girl, began competing over everything. It appears this girl is more aggressive, mine more hurt from this and has just become totally distraught over the loss of her friend, as well as the ones she keeps taking away. The friend is very cruel to my daughter, and I do know my daughter didn't know how to deal with this and lashed out to her in a defensive reaction, but I am sure too much, too often. They cannot be around each other now, and I cannot talk to her mother about it. It was too much while she delt with her husband dieing, (2.5 years worth of it). I am not sure how to help my daughter. I have said many things to help her, which seems to be alright, but I am just tired of hearing these stories of how every time she begins a new friendship, this other girl cuts in and bad mouths my daughter until the new friend is disinterested in my daughter. I'm not sure if my daughter can handle the situation, and I want to help her more. I did have her join a group called Side by Side. It helps kids with some of these issues, so will see how that goes. My problem is, I almost want to move her to another school. I know it sounds unrealistic, but is it? My daughter is gifted, and in advanced classes, earning her red belt in karate (her decision, not mine BTW) and plays intermediate piano (my decision, not hers :( (I tell her this was her main chore that I ask of her, that we give her plenty, and she has this as our reward. ???)  I feel like I don't know what I am doing here. Hope you understand and can help. I have been told by other parents that they cannot stand my friends kid because she is so cruel and mean, so I think my daughter is authentic in her claims.