I suffer badly from anxiety and I am extremely shy. I know that this comes across to people as me being aloof, but I just don't know how to have conversations with people.
I get very nervous, but the one thing that always suddenly seems to make the nerves vanish is if I get angry.
I'm afraid in your shoes I would have been rather angry and when I get angry there is no stopping me. I'd have stood up, vented about how cruddy she was to you, reminded her that the 30 mins was up long ago, told her how rude she was and likely walked out.
I don't know what a curves class / meeting is at all - but I'm guessing some kind of diet program? Quite honestly, having done weight watchers previously (and found it good with the exception that I didn't like the woman running my local one) I recently started something very different.
I went to see an Ayervedic homeopathic guy - he questioned me, told me what my dosha was and told me what was good and bad to eat to match my dosha. I've lost 30lbs. The biggest thing? Cutting out bread (all wheat products), sugar and soda drinks.
Anyway, massive sympathy from me, I know how horrible it is when people make you feel like a complete outsider.