Does Fey Ancestry give advantage on saves to break an existing charm effect?

Question

My group left the game last week in a tight spot. At the beginning of the encounter, a half-elf PC failed her save against a Vampire's charm - even with advantage, thanks to the half-elf's racial Fey Ancestry trait:

You have advantage on saving throws against being charmed, and magic can’t put you to sleep.

The vampire's charm effect states:

Charm. The vampire targets one humanoid it can see within 30 feet of it. If the target can see the vampire, the target must succeed on a DC 17 Wisdom saving throw against this magic or be charmed by the vampire. The charmed target regards the vampire as a trusted friend to be heeded and protected. Although the target isn't under the vampire's control, it takes the vampire's requests or actions in the most favorable way it can, and it is a willing target for the vampire's bite attack.

Each time the vampire or the vampire's companions do anything harmful to the target, it can repeat the saving throw, ending the effect on itself on a success. Otherwise, the effect lasts 24 hours or until the vampire is destroyed, is on a different plane of existence than the target, or takes a bonus action to end the effect.

Cut to the end of the fight. The charmed character is unconscious. She was taken down by the Vampire's summoned wolves, had two failed death saves, and then rolled a nat. 20 on her turn, coming back with 1 HP. I'm going to give her a chance to make her save against the charm effect again when the session starts on Thursday.

By RAW, does Fey Ancestry give advantage to a charmed character making the save to break the charm effect?

Answer 1

Yes, Fey Ancestry would grant advantage

Jeremy Crawford provides a clear answer to this question here:

Does "Fey Ancestry" apply to any spell or spell-like ability that gives the "charmed" condition?

Fey Ancestry benefits any saving throw meant to stop an elf from suffering the charmed condition.

From his wording, it's clear that Fey Ancestry would benefit the half-elf character in your case. The advantage on saving throws is not merely on saves that, if failed, would impose a new charmed condition; it applies to any saving throw that, if successful, would result in the character not being charmed. This would include saving throws made to break free from a charm effect.

Answer 2

Yes

You have advantage on saving throws against being charmed (PHB 23)

This includes any saving throw which results in the character being charmed if they fail it. That they are currently charmed is not relevant. Thus they roll with advantage went first getting charmed and also when trying to break it.

Answer 3

RAW - Yes, I think

Fey Ancestry

You have advantage on Saving Throws against being Charmed, and magic can’t put you to sleep.

While your Elven character is already Charmed, she is still making a Save against the Charmed effect.

That said, even if RAW said "No", you as the DM have the authority to allow her to still have advantage regardless, if you want her to have advantage. Just be sure to express to your player that they should roll with Advantage so that they can do so accordingly.