I think you might be overly sensitive except to the lesbian's mean look and that couple who avoided you big time. Can't say for sure about this lesbian, but many (some?) of them are biased against transwomen, whom they feel appropriate the female identity. And that couple might have had dinosaur attitudes in keeping with Archie Bunker. I suppose there will always be a few people in every crowd who refuse to get it.
That said, most people are a little leery at first of people or situations they are not familiar with and I think this is natural. So IMO it will up to you to be proactive and make it fun, like Bree says, and engage in friendly business chit-chat with people.
Two other observations: I know that you like to dress up (and you always look nice), but maybe next time you could do business casual? Maybe you won't want to create as much of a visual separation from the others with the clothes? Also, maybe next time you could sit immediately beside someone who is already seated and start chatting with them?
I'm very sorry that you felt bad and I hope that the next seminar will be more pleasant.![]()