Hmm ... was the treat very high in sugar or anything? I can't really imagine a single treat doing this to a rabbit... but take it out, just in case
It sounds as though she just had a fright. Did you open the door suddenly, or something? Could it have been possible that you hit her accidentally with the door when you opened it? (I'm just guessing there's a door where she was).
It's alright, I know how you feel. My rabbit Ollie is absolutely terrified of anything touching his back legs. Once while we were out in the wide open in my backyard, and he turned suddenly, and, before I could do anything about it, he had managed to get the leash tied
tightly around one of his back legs. He was absolutely terrified, and ran at top speed, colliding with a fence, before falling on the ground and going into something very much like a seizure. He lost control, and was spinning and rolling at such speed at I couldn't see which was his face and which was his legs. He was letting off little squeals of terror, but as soon as I placed my hand on his bac khe stopped, and calmed down a bit. I picked him up, and it took me half an hour to untangle him from the harness. He's fine now, but that really freaked me out. Luckily he wasn't hurt.
Enough of my story: how's she coping now?
Rachel.