FALL OUT? Heck, this baby is going to half pass it's way out and go straight into a piaffe. You'll be lucky if it's riderless! LOL!
It sure does sound like she's ready, though. If it were me, I'd be camping out. Mares don't necessarily change their behavior just prior to foaling. My mares ate right up till the time they were ready to start pushing. None of them really did any butt pressing, per se, but they did swish their tails a little more often as the contractions got stronger, and they would constantly shift from one hind foot to the other with an occasional belly kick. If you see Tenakee doing that, you can be sure she's not irritated by a fly. Also, her milk should be white by this time. You can also check to see if she's lost her mucous plug, which may be stuck to her tail hair, or will be blobbed on the ground. This is why it's really important to keep her inside now as much as possible so you can look for this telltale sign.
Good luck!! I hope everything with this foaling goes flawlessly, and you have a beautiful, curly filly by morning!