Yeah, buting a sore horse on turnout is usually not a good plan, unless they absolutely *need* a touch of bute to reduce inflammation. Oh well, now you will remember next time

, and it sounds like no real harm has been done.
It sounds like your footing is somewhat icy in front of the fenceline. You can do what Free says if you have bedding, but if you don't (your horses just live outside, yes?) another thing that works at least as well is to rake up as much manure as you can possibly liberate from elsewhere in the paddock and spread it thinly in front of the fence. Not right in front of the fence, but like six feet out or so, to give extra stopping distance. You may need to use a shovel to chop some of the frozen manure piles apart to rake them up. At first when you spread them they'll just be lying loosely on the ice but after a day or two of this nearly-0-C weather we're having they will weld themselves to the ice and provide pretty decent traction.
In fact if you have any Known Icy Spots, IMHO it is worth doing this periodically through the winter as a preventative, whenever there's a warm spell that makes it easy to acquire still-soft manure.
The manure spread on the ice will also slowly start to melt holes and roughness into the ice as the sun shines on it, which provides extra traction.
Good luck, have fun, hope she's feeling better soon,
Pat