I'm sorry!! You had to go through this!! Its ignorant people everywhere and as adorable as she is, they are just jealous!!
My pride wouldn't let me go back to that class too but its up to you. It sounds like you had a hard time finding a good trainer!! If I had no choice but to go back I would just ignore their comments!! If they continue maybe ask a question about their dogs so the attention can be deviated from you to them.
Good luck to you! I'm so proud of her doing so well! She's adorable and one of my favorites on here