
Hi ceejay,
I agree with Em - seems more likely that Meg is insecure without you or your OH around and gets 'tough' when she feels she has you back her up. I'd try to work on her confidence levels both without other dogs around and then gradually with them.
Unfortunately the environment in some agility classes is too hyped up for some dogs and she may be a little overwhelmed just now. Perhaps take a break and gradually reintroduce classes when she has learned better to cope with all the hullabaloo.
Can you distract her with food and, ideally, a toy when other dogs are approaching in routine situations? If her focus is less on other dogs then perhaps she will gradually come around to largely ignoring them and then you will have a better chance of success when she is in a really dog congested area.
HTH, Teri