I totally understand AMI not being comfortable with large crowds. Sometimes people can be quite overbearing. Not to mention the fact that I rather see her like Jonathan Frid:
Would I like to see them at a fest? Who wouldn't?! But the fact that they haven't come for some time would only make their lines longer and their time there more grating and slow: Imagine the lines of people who would want autographs, pictures, to ask questions, share personal stories, etc etc. The lines with LP were bad last year, and these lines would be 10 times as horrible, I'm sure.
It doesn't mean they're snubbing the fans, but the fact of the matter is that if they DID attend, it'd be a madhouse to get to them. There's no telling what fans would do to get a minute alone--follow them to their room, interrupt their meals, follow them into the restroom, etc etc.
If it were me, I'd be hesitant to attend as well.