Welcome to the world of the dance diva. She is immature and short sighted (upsetting a paying client) but this is not uncommon. You have insulted her, first by switching instructors and then by not dancing with her at the party. Find another studio.

I don't think you have anything to apologize for, personally. As a manager of a dance studio, I wade carefully through the fields of dance ego on a daily basis. There is always an instructor upset about someone or something. The more professional never let on to their students when they are pissed. Others have dumped well paying customers because they feel they aren't valued enough by the student. It is beyond tiresome when I have to talk some instructor down off the hissy fit ledge. So what do you want? If you want to stay at that studio, talk to the owner, ask her if you upset her in some way. As far as the parties go, Salsa is only one of many dances. If she plays too many, she will get complaints. My advice is to learn other dances so you don't sit out so much. Or find a salsa club or group in your area that dances it exclusively. If you act weird around her, then she will ignore you. Continue to be pleasant and it will blow over.