Right-on, it's good you're conceptualizing.
It's always a good idea to have a rough outline of what the final product will look like. Storyboards are one way to do it, through visual medians, but animatics can explain certain actions better than a storyboard at specific times; it's all situational.
Since we, the audience, don't have a script, storyboard, or anything else to work with to know where the story's going, I gotta ask...is that how the animation will end? Rock abruptly stops near edge of the cliff, and the force of inertia catapults the bunny into the adventurer girl propelling them both into the body of water?
We got the conflict, but that's sort of a weak climax...I feel like I watched the first 1/4th of a short animation. Although I was prepared for corners cut in the visuals, I wasn't prepared for corners cut in the content.
If you just wanted to show your friend the animatic, you could've uploaded it to NG's dump, and sent him the unique web address through a PM or an email, but since you uploaded this to the flash portal, I'm assuming you're looking for constructive criticism.
Music's good. Sound effects are acceptable. I would revise the bunnies extreme-close-up paw, and make it look less carnivorous and more like a bunnies paw...or if not that, make it more cartoony and anthropomorphic..I would just ditch the emphasis on the claws (yes, I know they have claws IRL, but they aren't like cat's claws)
Moreover the woman's shrieks were shrill and sure annoying. Huffing while running, while occasionally looking over her shoulder with an "OH NO!" "shiiiit!" or just the OCCASIONAL scream would suffice; all things in moderation. Plus, you'd think if she was sprinting ahead, screaming at that CONSTANT RATE would exhert too much energy. Again, it's a cartoon, so you got room to be whacky...I'd just tone it down a bit for the sake of being less annoying.
Additionally, you could up the funny by having the Bunny scream only when exposed from the rock. "AAhh!!-...aaAAAhhh!!-...aaAAAAhhh!!-
..." Y'know? Like a merry-go-round of PAIN.
Good effort; submit the finished product when you're done!