sounds like it could be frostbite with the black..
could be no circulation..
could be an injury what with the bloody bottom.....
make this up for her..
layer feed with a little water cooked oatmeal, plain yogurt, chopped cooked egg, a crushed Tums.
make it so it puffs, not soupy.
make up enough to give 2 or 3 feeds for the day..and give for a week, along with access to regular layer feed..
(give the crushed Tums only once.
see if she improves.
give vitamins and electrolytes in water..the electrolytes for a couple days..continue with the vitamins..
if you don't have poultry vitamins..you can use Poly-vi-sol baby vitamins..2-3 drops in beak once a day for a week, then taper off.
you can try putting polysporin or neosporin on the foot..
or if you can get some Panalog or Animax..(treats both bacterial and fungal infection)..
or you can alternate a few days each..with neosporin and any antifungal ointment, such as for athlete's feet.
wouldn't hurt to wash the legs/feet..very diluted gentle soap, and rinse and dry.
you can also give plain aspirin..1 (325mg) tablet crushed in 1 quart of water..might help with discomfort and circulation..
do you have any antibiotic on hand?
poor thing sounds in bad shape.
others might have different suggestions for you.