circumstantial evidences based on your side of story do not give any proof of racism taking place to me. rude, perhaps. could ISM have better? absolutely.

but escalating this will lead you nowhere apart from wasting your time and further angst of inaction. i would suggest you just move on, like any other grief in your life.

next time if you want to pursue such claim, perhaps take recording. unless ISM called you by racial deragatory comments on recording you have zero luck... but if you did you can end her career there. good luck