often do change. They are still really young at that age and learning to deal with emotions. My daughter was bullied pretty bad in first grade but later became friends with the girl because the other girl grew up and matured. At the time we were super frustrated, but the teacher just told us that this is common at that age. I thought it was a mean girl, but it was really just a first grader being a first grader.
Some people who are bullies later in life are more set in their personalities though.
But yeah at this age, I'd focus on your daughter learning to cope and letting the teacher know to keep an eye out for it.