B.S.
Could you help out in the classroom? If so I would stress, that it would only be the determined days or the determined amount of time. Also that she can't hang on you, as you have to help everyone. And that if she breaks those rules, you will no longer be able to help. Maybe then you could take that opportunity to help her make a friend or two.
My daughter is VERY shy and had a tough start to preschool...but it did get better. It doesn't always happen over night. My daughter was STILL in November opening up to her teachers/classroom but they said every day was getting a little better. She is now in 1st grade and that first year of preschool did help her tremendously. In fact she had no issues starting Kindergarten last year, even her preschool teachers were amazed at how much she had grown socially.
Have you tried role playing with her at home. Get a doll house, ponies or something similar and play out school. Specifically the playground and areas she has complained about. Take the doll and have it look out into the areas she talked about to find a child not so rough or not fighting. Find a friend who is quietly playing. I know role playing with my daughter in the past has helped a lot.
Good luck....I wouldn't give up.