Is there any way of appealing against the grade? It does seem very unfair that you were assessed in a foreign language while being undermined by the intern. Sometimes it is best to walk away from unfair situations but sometimes you have to fight your corner. Unfortunately the only person who can decide what is best is you. I hope you find a way to move forward.

I have great respect for your ability to communicate in English when it isn't your first language, you manage really well, don't let bullies like that teacher affect your confidence.