Oneshot, slight AU. When Bellatrix goes in for the kill, she sees her little sister staring back at her.

"Aww, poor little Dora," crooned Bellatrix as she stepped forward, eyes glinting. Dolohov gave her a nod and left, making her smirk. Even that fool knew better than to be near when Bellatrix Lestrange was playing with her food. "Did your little wolfman die?"

Nymphadora Tonks didn't reply, cradling the body of Remus Lupin in her arms. Her back was to Bellatrix, but the older woman saw her shoulders shaking and her hair turn to a mouse-brown color. Idly she noted that it truly was a pity the girl was Mudblood spawn, because really she was talented…"You know, it really is better this way. It saved me the trouble of killing him myself." Tonks tensed but made no movement. Bellatrix smirked—Almost there—and pressed forward, ruthless, cunning. "And after I kill you, how about I go after your mummy, hmm? Andie's repayment is long overdue. Oh, and of course I mustn't forget that little brat you gave birth to, he certainly can't be allowed to li—"

"CRUCIO!" In a single movement, so fast Bellatrix almost didn't see, Tonks leapt to her feet, whirled and fired the curse at her aunt. Bellatrix was hit but merely stumbled back with a snarl.

"You have to MEAN it, girl, didn't anyone ever teach you anything? This is how it's done—CRUCIO!" Almost as fast Bellatrix roared, but the young Auror simply dodged.

"You WILL NOT touch my son!" Tonks spat, eyes flashing furiously. "I will KILL you before I let you near him!"

"Aah, are you worried for your itty bitty baby?" she sneered, laughing cruelly. "Don't want to let Big Bad Aunty close? You little dirty half-blood, your child is part werewolf. He doesn't deserve to live."

"YOU don't deserve to live, you monster! Tonight Voldemort loses his sadistic whore."

Back and forth they battled, exchanging hexes and curses. Bellatrix hadn't expected to actually have to TRY, much less pay attention to what was going on. Andromeda's daughter, dirty-blooded as she was, possessed a very high level of skill in dueling. But she was Bellatrix Lestrange, she did not lose a battle to half-breed filth. Spitting in fury, Bellatrix slashed her wand through the air. Tonks didn't react fast enough, and she crumpled to the floor, wand falling from limp fingers.

Fury and bloodlust pounding through her veins, Bellatrix screamed in exhilaration, preparing for the glorious moment when her worthless niece would finally be erased and the House of Black would be pure once more. She aimed her wand into Tonks' face, waiting for the young woman to open her eyes so she could see the terror and pain in them.

But when Tonks did lock gazes with Bellatrix, her eyes sent a jolt through her aunt's veins. Because Bellatrix knew those eyes, knew them better than her own. She had seen those eyes every day for nearly twenty years; seen them shine with joy, spark in anger and glisten in fear. Bellatrix had seen those eyes hard and flat as they turned away from her; she had seen them shining with affection as their owner giggled and tossed their arms around her neck. Bellatrix had loved those eyes more than life itself.

No, not Bellatrix. She hadn't been Bellatrix then. The old nickname echoed through her skull, a distant cry of the long-gone past only used by the one person who remembered. Bella.

"Andie." Without her realizing it, the name slipped from her lips. Bella's wand began to sink unknowingly as her entire frame shook. The body, the face, the hair—it all belonged to the half-blood freak. But Salazar, those eyes—they were Andromeda's, completely Andromeda's, and Bella loved them fiercely even after all this time. Seeing them again simultaneously caused the chasm in her chest to close and ripped it open again, spilling out hot-hurt-hate-pain blood.

She couldn't. Merlin forgive her, she couldn't kill Tonks. Not with Andie's eyes staring at her that way. Andromeda's smile, her laugh, her voice; they all danced in Bella's mind, memories tumbling over one another, all showing the girl who was the other half of her older sister's soul and never even knew it. And if she did, it hadn't been enough.

She backed away, trembling from head to foot, every nerve in her body screaming to kill. Bellatrix Lestrange wanted to murder that little half-blood. But Bella Black couldn't.