M.R.
What are you giving up on? Your daughter sounds like she needs exactly what the school said, it is what you said yourself, she needs practice to learn to play with other children. You should ask for this from the school counselor, they run friendship groups and friend ship classes all the time. Your issue is that your daughter has few friends and they must be of a certain quality for her to find interesting and they have to accomodate her intensity, and.that is a great deal to ask of 5 year olds.
The "old girl" who your child was "associated with" (? does not sound like a ringing endorsement as far as friendships go...) was not under contract to be your daughter's exclusive play mate, she was free to make new friends. Three is very hard, and most children need some help and coaching to understand how to navigate it, especially when there is some ridgity from one party, that being your daughter.
If no hitting or kicking occured, you have nothing to worry about. This is a school issue, and since no diciplinary action has taken place, I would take the high road and just assume it never happened, because as far as the school is concenred, it never did. I would write, not speak, but write to the principal and ask for help for your daughter with the counselor, and very nicely state that you are uncomfortable with the attitude expressed to you by the parents of "new girl" that she is to retaliate violence for violence, and that you think that all the children should be instructed in school and at home that hitting, kicking, etc. is not acceptable and that you hope that the issue will be addresses with Mr. and Mrs. new girl, so that they also stop giving thier daughter instructions to retaliate violence wtih violence. It is quite possible that they already have, but you have zero right to know what they have said to Mr. and Mrs. New girl, just like they have zero right to know what the school has said to you.
In any case, this is not a police matter, and certainly, not against the room Mom. Let me share with you a perspective of a Mom who has a child who is bullied. She is bullied because she is mentally retarded and she has autism. That sounds horrible, and it can be, but why does this happen to her? Sometimes, it happens to her because kids are just fed up with some of her behaviors, and for what ever reason, they just do not want to put up with it at that moment. You know, I can't always blame them. It is in the way that they do it that I blame them, and that I always ask for help from the school to teach other children the right way to express themselves about very valid issues. I also take the opportunity to use every example of "bullying" to look to my child and what services I can get for her such that she does not draw this kind of behavior. Nasty is not OK, but feelings, like two girls who have hit it off and want to play a game that is not so "intesnse" is not forbidden, nor should it be. They all need "practice" because they are only 5 years old. Get your daughter the help she needs to be able to find all other children suitable playmates, and when that happens, she will be much happier.
M.