Do we have a bully on our hands?

As usual I picked Lauren up from school today and she would not tell me what she did. She just kept saying "I dont know" well I kept on and while we were eating lunch I asked if she cried today and she said yeah because I pushed my friend off the seesaw! I asked why she did that and it was I dont know. Then I asked if she said sorry and she said NO! I asked if the teacher got on to her she said no to that also but I know they had to have or she wouldnt have been crying. The teacher didnt say anything to me about it. This girl has a mean streak in her!!!