In the first pic it is hard it looks more like a bacterial infection, but in the bottom pic, it does have the appearance of frostbite with some swelling at the tips of toes and the discoloration and swelling. I would get some hibiclen (chlorhexidene) or some betadine and add it to warm water, and soak the feet daily for 15-20 minutes. Then apply either some Vetericyn wound spray or plain Neosporin or Bacitracin to any open scabs. I would also try to get some enrofloxacin or Baytril from your local vet. You can get it online, but would take too long. Here is a link for that and another about frostbite and one for bacterial infections in feet:No tissue is turning black. I'll take a picture and try to upload it. She did break the blisters and scratched it yesterday.
Today there is an odor and the skin is peeling.
