I insulted my son's headmistress, what trouble could I have caused?

My 7 year olds headmistress called me in to see her yesterday, she said that my son appeared sad and withdrawn at school. After speaking to my son about this, he told me a certain child had been verbally bullying him, I had told the headmistress several times over the last two years about this child but always got the same NO TOLERANCE speech from her, nothing was ever really done. Anyway, yesterday the headmistress interrogated me as to why my son is unhappy. When I told her it was because of this child bullying my son, she did not want to accept it and asked me questions regarding if im treating my son well, if I hit him, if anybody could be abusing him etc. Im a single mother that lives alone with my son, his father walked out when he was born. I have never mistreated, hit, neglected or abused my son ever and to have the headmistress saying this to me made me angry. The way she spoke seemed patronizing like she refused to believe that I was not causing my child any harm or misery. Towards the end of the conversation I had enough of her accusations and I admittedly lost my temper. I said to her.. "that she should have better things to do than accuse innocent mothers of upsetting their child and she should do something more productive like go to the gym". (she's very obese) I also said that.. "she was a hypocrite for promoting healthy eating in the school while she is the weight she is" I know it was a stupid thing to say/do but it was a spur of the moment and I am under a lot of stress at the moment with university work. I'm now worried to what she could do because I insulted her. could she kick my son out of school ? be hostile towards me and my son in future ?