Graveyard of the Weeping Willow encounter

This is an idea that have grown in the back of my head. Feel free to discuss consequences, use your own take on it, or suggest variations of ideas.

As the party wanders through the forest they will begin to hear a voice singing in sylvan during night. It is beautiful in tone, yet carries with it feelings of sadness.

If the party wishes to follow this voice they will they will come upon a forest clearing with a pond. In the midst of the pond is a great weeping willow and below it sits a woman in white kneeling before a man lying on the ground. The man appears to pale, badly hurt, yet peaceful in his face expression.

If the party pays attention to their surroundings they will notice that there are several overgrown rocks, both on land and in the pond. A closer overation will reveal that these are dead soldiers wrapped in vines and overgrown in moss. Several of these will appear to have died from arrow wounds, but not all of them.

How the encounter can go:

- If anyone in the party speaks sylvan, they will recognize the song of someone lamenting a lovers death, the bravery of a man standing against many, a sacrifice to protect the dryad against soldiers seeking to harvest her magic. A warning against those who come to despoil her glade.

-If anyone in the party speaks elven (or if they are a bard), they will recognize the song as one of sadness, but failing to grasp the direct words.

-The woman will not be hostile towards the party, but will gesture for them to stay back unless the party manages a diplomacy check.
If they continue forwards she will be frightened and disappear into her tree.
(Depending on character level, consider having a Wood Woad appear as a guard. Alternatively nixies in the water.)

-If the party stops the woman from singing, all the overgrown rocks will awake as undead which will attack the party. They are not controlled by the woman.
Suggestion depending on character levels: Skeletons, led by a wight.

-If the party uses detect good or evil, they will know that the mounds are undead and the woman in white is a fey.

Aftermath of battle:
-If the party used turn undead or holy water on the undead before talking to the woman, she will recognize you as friendly. She will allow you to observe her lover. (Human/elven man. Appears as a soldier. Carries with him a sword and bow. He is as if someone had cast gentle repose on him.)

-If the party killed the woman in the process, the willow will wilt, the glade will turn black and the party earns the hatred of a treant.

-If the party scared the woman, but used revivify on the dead body, the man will ressurect and the woman will consider the party as friendly. Consider giving the party a great boon.

Background:

A hundred years ago a man fell in love with a dryad. He told his friends about it, but they misused his trust and wanted to use her magic for their own. They went out to kill her, but they had not accounted for the mans martial provess.
The fight was hard and brutal and the man was dealt many fatal wounds, yet at the end of battle he was the only one standing only to perish in the arms of his beloved.

Yet, many years later, the hatred of the soldiers still inger, only kept in check by beautiful song of the dryad.

Characters:

Deidre: Dryad of the weeping willow. Her song has a calming effect and thus her grove is untouched.
Tristian: A man who fell in love with a dryad. He is a good man, though with a terrible choice in friends.

Marcus: Leader of the band of soldiers. Possibly turned into a wight.