@kimberliegbisho gives a good example...my experience is very similar.
Tho I'm not in Vermont we had a couple of frigid winters in '13-'14.
Your hen looks like she might have some very mild frostbite...which can appear as a grayish white and will 'go away' with no tissue loss.
The black stuff is dead tissue from severe frostbite...the black portions will eventually fall off and not regrow.
IMO coating combs and wattles might help prevent frostbite, but there's no guarantee it will prevent it....
...but once they have it, it's best to leave hands off unless they have an obvious infection that would need treatment.
Messing with compromised tissue can just make it worse and actually introduce infection.
There can also be swelling that can last a few days.
This guy healed up just fine with no intervention, tho I did keep a close eye on him for signs of infection.
He lost his comb tips the year before and lost parts of his wattles from the event pictured.
By spring you could hardly tell what had happened.
Initial swelling, lasted 2-3 days.
After swelling went down.