Much like Oleandra's sneaky spells, which all used the Perthro rune as their core, causing them to unravel the moment she was found out, the protective enchantments surrounding The Burrow shattered the instant the enemy forcefully became Secret Keepers.
Despite its remarkable ability to conceal secrets within souls, the Fidelius Charm was only as reliable as its Secret Keeper. When Dumbledore died, everyone privy to the secret became a Secret Keeper in turn— free to pass on its contents to whomever they pleased.
And considering the not-so-small number of wedding guests and Ministry officials who knew the location of The Burrow… when the Ministry fell, it didn't take long for the Death Eaters to cop hold of someone in the know, force the secret out of them, and become Secret Keepers in turn.
…
Time seemed to slow down to a snail's pace.
The few brave souls who hadn't yet fled were now sprinting madly in all directions— The Burrow was no longer safe, and anywhere was better than here. Chaos gave way to pandemonium, forcing the members of the Order of the Phoenix to lower their wands, lest they curse an innocent wedding guest by mistake as they ran around like headless chickens.
Before Oleandra could stop her, Hermione grabbed Harry, Sirius and Ron by the arm and spun on the spot, Disapparating with a loud pop. Oleandra's eyes narrowed as she spotted Ginny's flaming red hair amidst the sea of panicking guests.
"Harry!" Ginny's anxious voice rang out from the crowd. "Where are you!?"
Oleandra started walking purposefully towards Ginny, backhanding some poor bloke running past her with her Lethifold-clad fist, sending him sprawling. Masked figures cloaked in dark robes started appearing one after another in the middle of the crowd and in the orchard surrounding them, blasting whoever was closest to them while laughing cruelly.
"Ginny!" cried Mrs Weasley, not too far away from Oleandra. "Ronnie? Harry?"
Total darkness hadn't yet fallen— it would be another ten minutes before the sun dipped below the horizon— but Oleandra's runic magic was already growing stronger by the second. Even so, the last thing she wanted right now was to get into a fight with the Death Eaters. She was in no position to protect the wedding guests, anyway— she was liable to get shot in the back by the Order of the Phoenix.
For now, You-Know-Who's faction knew Oleandra's stance towards them was ambiguous at best, and she wanted to keep their attitude towards her as neutral as possible until she could decide how to move forwards with her plans.
"Mollywobbles!" Mr Weasley's voice rose over the din of stampeding feet and screaming. "I've got Bill and Charlie and Fleur! Have you got Ginny?"
Ginny ducked low, searching in vain for the Gryffindor Trio.
…
To Ginny's dismay, Dumbledore had died before he could fully explain what Harry should do with the Horcruxes once he had collected them all.
At that point, the old man was meant to reveal to Harry her true identity as half of Tom Riddle's soul— forcing him to acknowledge her as the Dark Lady, since she also fulfilled the conditions of bearing a wand of yew and was an abomination in her own right. Then, she would put Tom Riddle's soul back together and ensure Voldemort could die a true death; fulfilling the prophecy's terms and saving his eternal soul and her own skin.
So far, Ginny had managed to collect:
1. The Diary— though the half-soul sealed inside had accidentally fused with half of Ginny's original, due to the profound remorse she felt when she realised what she had stolen from the Weasleys. She would have to murder in order to split her soul apart again.
2. Marvolo Gaunt's Ring— recovered from the shack in Little Hangleton.
3. Salazar Slytherin's Locket— retrieved from 12 Grimmauld Place… of all places.
4. Rowena Ravenclaw's Diadem— found in the Room of Requirement, and now parasitising Gilderoy Lockhart, though it had not fully taken over his body on Ginny's orders.
This added up to four soul shards.
Still missing were:
5. Unknown— Dumbledore and Ginny theorised it to be Helga Hufflepuff's Cup.
6. Daphne Greengrass— the last of the intended six Horcruxes, which Voldemort had originally planned to create by murdering baby Harry— only to be struck down by his rebounding Killing Curse before the ritual could be completed. The soul fragment had first been sealed within the female Maledictus Nagini, but was later transferred to Daphne in order to preserve the magical number seven and fulfil the terms of the second prophecy.
7. Harry Potter— the accidental seventh Horcrux.
8. The Soul in the Bottle— the unintended eighth Horcrux. A Horcrux's magic prevented any part of a soul from passing through the Veil, so long as one still existed to anchor the others to the land of the living. This particular fragment had flown out of Oleandra Greengrass when she walked through the Archway in the Department of Mysteries two years ago to recover Sirius's body. Dumbledore had contained it in a special bottle— but after his death, the bottle was found neither on his person nor in his office. It had simply vanished into thin air.
Funnily enough, this last Horcrux had allowed Voldemort's soul to finally find some semblance of balance, as it was now divided into a total of nine pieces, including the one walking and talking in his noseless body. In numerology, the number nine of Northern Europe was no less magical than the number seven of Western Europe.
It was much better than being stuck at eight, at any rate.
Thus, Ginny now faced a dire problem: if even one of the missing four Horcruxes were destroyed, Dumbledore's entire plan would go up in flames. She had hidden the locket and the diadem somewhere he would never find them— as insurance against him betraying her— but now that Dumbledore was dead, and Harry's gang lacked the full context, they were certain to hunt down the others with the intention of destroying them.
Ironically, because Ginny had wished for Harry to learn her true nature as late as possible, Dumbledore never instructed the Gryffindor Trio to include her in their Horcrux hunt. As a result, Harry, Ron, and Hermione had set out without her, hoping to protect the younger girl from the dangers they knew they would face during their quest…
…
"NOOOOO!"
Ginny swivelled, recognising her mother's scream.
Tendrils of darkness enveloped her as Oleandra extended her hand towards her, clad in her Lethifold's shadowy folds. Ginny had no idea what Oleandra could possibly want with her, but it was clearly nothing good.
Ginny wanted to fight, take back the Soul in the Bottle, if Oleandra had it— but in this state, Oleandra was nigh invulnerable, covered in layer after layer of magical armour, runic wards and invulnerable Lethifold hide. Her brilliant mind flitted through the possibilities: cast a Patronus to scare the outer layer away and work her way through the next two, cast the Killing Curse and tear through the wards like rice paper, or…
Run away and take the fight elsewhere, allowing her to go all out without witnesses!
Oleandra grabbed Ginny's shoulder as the younger girl spun on the spot. Suddenly, Oleandra felt as if a hook had lodged itself in her bellybutton, hauling her up through a tight, sausage-casing-like tube… and then both girls tumbled out into a field of white flowers, just as the moon above reached its zenith, casting its gentle radiance upon them.