Help Tink get diagnosed

Tink has been fighting an unknown skin issue and the local vet is stumped. She had a toe amputated this summer due to this mystery condition and she really needs to see a specialist.  Unfortunately,  funds are tight for her fur mom and Tink will likely have to be euthanized if she doesn't get the proper treatment soon. Her fur mom has tried every home remedy that has been recommended with no luck. She now feels that she has run out of options. Please help me help Tink. Her fur mom has suffered devastating losses already over the past year or so and she cannot fathom losing Tink.