have a heated waterer in the coop
I don't leave water in the coop at night. It just brings more moisture inside. I take it out when they go to bed & return it in the morning when I open, just past sunrise. I know it's probably too late to get pics tonight, but maybe tomorrow take some of the ventilation you have & get feedback. I thought I had plenty of ventilation but 1 girl got her comb tips frostbit so I added another gable vent. There's been 2 more freezes since & no further problems.
I'm sorry you're having troubles. I agree with @Hamiam Is there a way to take out the water container at night? This may be contributing to moisture in the coop.
Moisture and exposure are both contributors to frostbite.
The vaseline won't hurt her, most likely it makes us feel better when we do something

Will wait for photos, but a lot depends on the severity of frostbite, points may blacken and fall off.
Look forward to your photos - I hope all goes well for you tonight.