bullying advice

So my 9 year old comes home from school and tells me this girl is her class pushed her into the table and elbowed her in the stomach, she said she told the teacher and the teacher said if your if your not bleeding or puking don't bother her! I call the school and talk to the principal and she tells me my daughter and this girl have been having bouts back and forth. Well the school requires you to invite all classmates to birthday parties not just select ones so I did and today this kid comes in and I thought it was a boy the mom introduces the 2 of them and I realize it's the girl that has been having problems with my kid. She looked like a boy dressed like a boy in the sense she wore a boys dress shirt and dress vest with slacks has a boys cut but wears lipstick and earrings. So then another mom is telling me her daughter has problems with this kid also and numerous other moms are telling me this and that the school is not handling the issue because of being afraid of a lawsuit for discrimination. So our children or being punished for reciprocating but this other kid never gets punished! I'm I taking this to hard? I'm not sure what to do but I'm not happy