Honestly, I wouldn't have discouraged your cousin the way it seems you did unless she really really cares and would have a trip ruined by not going to a specific restaurant...and I guess to that I'd say if your trip is ruined by not getting to eat at a specific restaurant to look at the bigger picture. You are in Disney World. It's hard to not have a good time. If I can still get things literally days in advance, I would guess there are definitely some workable options for 2-3 months in advance. *shrug*
Huh? How did I discourage her? I think you took this way too seriously. And no, if I couldn't eat at particular restaurant, it wouldn't ruin my trip. I'd simply find some other place to eat, no biggie!