Starting to sound like frost on the wings and a F/A not being convinced this is within the limits of cold weather operations for some aircraft.
Good she spoke up but when the F/O explained that it was ok she should have accepted this, if still in doubt she should have voiced her concerns to the Captain.
Lying to the cockpit is never a good thing.
All credibility is out the window after this for her and the cabin crew.
Light Frost is not much of an issue, snow ice buildup is!
Good luck to the F/O, seems he had to spend some money already to defend his self.
If this is true and not more to the story he should be able to recover it as it seems he had to put out a lot to defend his self.
And deserves it!
CRM could have been much better, but for some its a lost cause.