Looks like the one foot is in the process of dying off and auto amputating, hard to see the other one.
Again, I recommend that you read the article and threads linked below. Lots of details, information and photos that will help you through this process.
Another current Frostbite thread...
Welcome To BYC
Can you please post photos?
Depending on the severity of the Frostbite, your hen may lose just a few toes to a whole foot, so photos can be helpful.
This article is one of the BEST resources we have her on BYC when dealing with frostbitten feet. I recommend that you read it...