Instead of just asking her to go, try to make it so that EVERYONE goes all at the same time. Then it's not a question of "do you need to go" but "everyone's going so that we don't have to keep going in at different times. Your turn!"

She might be getting mad at you and refusing to clean up afterwards... but you know, that's probably more embarassment than anything else.

Just try to respond compassionately, have extra clothes around at all times, and maybe swap to the older-kid sorta pull ups? (what are those called? The good nite things?). It's a new behaviour for her, so it's likely just the excitement and stress of being somewhere cool. She's likely never done anything as fun and just doesn't notice the bladder.