this is tricky. Because reality is that at 4, what to them is name calling is often just calling them something different, ie two of the kids my ds plays with got into the habbit of all calling each other buster or something similar and one took exception and said that she was being called names which in fact she wasn't. But to her it was upsetting whereas to the other children it was just a bit of fun with no malice.
If these children are being violent though I would definitely encourage her to talk to the teacher. Violence of any kind is not tolerated at my ds' school and if your school is a decent one they should deal with it.
I also think that cliques are quite common, esp if groups of children have joined the school from a preschool where they all knew each other, they tend to stick together iecause it's a bit like safety in number iyswim, and often it's difficult for other children to break into that circle. Again in our school the children that have come into school together are encouraged to play with other children after half term when they've settled in, are given group activities etc to do without their usual friends so as to encourage them to be open to other friendships as well iyswim.
4 year old friendships are very fickle, and what might not be her best friend today might be tomorrow and vice versa.
I certainly wouldn't go round threatening 4 year olds that they'll be sorry if they lay a hand on your child again.
I would encourage your dd to walk away and play with someone else if these girls don't want to play with her, and if they hit her to tell the teacher.