Bunnie, you have an undisplaced fracture of the tip of the malleolus. As your ankle was pushed over by the horse, the ligament pulled a piece off the tip but it remained in place so should heal well.
With your symptoms I think there is no chance of you having RSD so don't worry about this rather unpleasant syndrome.
Normal healing time for this fracture is 6 weeks, and you can't really hurry it up however you try. Keep wearing the aircast and I am sure you will keep weight bearing on the ankle as you are keen to be active! As long as your ankle does not go over you should be fine. Overall you might find it takes 10 weeks from the injury for your ankle to feel fully good again.
Good luck!
Jonathan
J Blood-Smyth
HPC Registered Physiotherapist
Physiotherapy Site, Local Physiotherapists, Qualified Physio