Puppy Won't Go Potty If It's Cold?

I'd like to know what to do, because I have a 4 month old Catahoula/Lab cross whom I had pretty well potty trained until the ground froze. Now she would rather poo in the bathroom and pee wherever. She has a spot over in some tall grass, but she has to cross our frozen driveway to get to it. There's something about frozen mud that she really doesn't like. I know its cold, but so is the rest of the ground. What do I do?

P.S. She won't wear booties

By Kayla & Aubrey from USA