If you put her in warm water bath.........keep the water warm, don't let it cool. When she comes out, dry her good (of course) but use a warm blow dryer to get that water off. A horse water-shed blade would also help take it off.
Let her lay on & cover her with a human blanket. If she'll allow you, put a heating pad on top of it, with you there, of course. Don't leave her alone with it unless you are VERY near by. I'd also lay her by a heating vent. In my OLD house, the heating vents are flat on the floor. You can even put the blanket she's laying on top of the heating vent without any problem.
Just please be near by and check her often. I'd be sitting on the floor with her.
Also, why not try some warm broth? Soup sure helps when we're cold. Warms from the inside out. Maybe a 1/2 cup or a cup? Make sure she gets water to drink too, since she could be dehydrated, even tho she was standing in the water, doesn't mean she drank any.
And if you can't get into see the vet today, at least call & see what else they suggest. Good luck with this. Please keep us posted.