Hi Katherine:
I had a similar problem with my daughter when she was 7: I even tried separating the girls for a while, you know, not letting them play together, but they insisted they were still best friends despite the problems. Sound familiar?
Talking with little ones at this age to "talk to the teacher" never seems to work: by the time the problems have gotten big enough to need the invovement of a grown up the girls aren't able to stop themselves and ask for help: in short, becuase of the stage of development they CAN'T ask for help.
I found just listening to my daughter and asking questions about HOW the fight started and how she FELT about the way it ended helped shed some light on the situations. Many times kids go through a pecking order stage especially if they start playing with other kids at school. Territory includes people and feelings. 8-)
Have you tried asking your daughter how she feels about the way her friend acts? How about the way she acts towards her friend? I tried to help Karen put herself in her friend's shoes and did some role playing with her teddy bears: practicing saying and doing things that would help create a more positive alternative to fighting.
Some times all we can do is pray and help the kids ride out the storms together.
Hope this helps. Keep me posted?
Ciao
K.