Quick note:
Okay so I don't have OotP in front of me so the canon quotes are from memory or from what I could find online... and I think one of the quotes is actually a movie quote but hey everyone loves Helena Bonham Carter. Enjoy!
I loved her more than I could ever love anyone else. Regulus was always a bit on the unconfident side, Narcissa spent more time looking at her own face than looking at where she was going, and I don't even want to mention Sirius, the traitor Gryffindor. No- she was the one I loved more than any of them. She had the natural Black family beauty without basking in it the way Narcissa did. That wasn't even their biggest difference. Narcissa would be fine in life because she could get any boy to do her work. But the one I loved was truly intelligent, truly powerful with her wand… She's the reason why Slughorn had such high expectations for Cissy. Her beauty was alarming in not the Narcissa, carefully groomed way, but in a way that could make even the smartest Ravenclaw boy at a loss for words with just a twitch of her lips.
The way the boys followed her at Hogwarts- I missed it ever since my lifelong engagement to Rodolphus became public- the boys never dared to trail after me by my seventh year. I would watch her walk down the Great Hall, with her chin raised just slightly above the horizontal (a maneuver I knew she picked up from me), silencing the hall in her majestic grace. Sure the Sorting Hat had taken just a bit too long to sort her into Slytherin. Sure when she wasn't paying attention she tripped over umbrella stands left and right. But when she was at Hogwarts, leading the suitors with incomparable grace and stunning the Ravenclaws with her knowledge, they called her a mini-me. A mini Bellatrix. And that's why I loved her.
But the woman standing next to me without the least bit of confidence couldn't be her. I watched her stare ahead, terror stricken, her wand shaking in her hand.
"Leave him, or I kill him," I hissed.
Her eyes stared back into mine- like a mirror with the most terrified version of myself staring back.
"Bella, you wouldn't. Bella, I know you- you wouldn't split your soul to do that to me- Bella, please!"
"Oh, did you love him? Did you love this piece of filth?" I snarled, slashing my wand at the already limp body a few feet away on the forest ground as a satisfying red gash appeared across his chest.
"Bella stop… yes I love him- he's not that different from us-"
"Not that different? You're pure… he has muggle blood running all through him, clogging his arteries, poisoning his veins!" I shrieked, swiping my wand again, causing another gash.
She tried to run to him, to heal him. I pushed her back with an irritated wave of my wand, letting his filthy blood spoil the soil of the barren forest.
"Leave him, or I kill him," I repeated.
"Fine Bella fine! Let him go and I'll leave him, I swear!" she cried, the tears looking completely foreign to her flawless face. The boy groaned on the floor, trying to get up but falling back down with a flick of my wand.
"Crucio him."
"W-what?"
"Then I'll know you mean it."
"Bella, that's an Unforgivable…!"
"It's easy- just point your wand and- Crucio!" I hissed, letting all of the hate I had for the filth stealing the one I loved away from me erupt from my wand and hit the body. It tried to suppress its screams, gasps of air escaping from it as its body squirmed on the ground.
"Bella stop!" she sobbed, grabbing my wand arm away, allowing the boy to pant for air on the ground.
"Do it. Crucio him and leave him forever."
She raised her wand shakily with the hand that so many worthy pure bloods had tried to hold, to kiss, the hand she had rejected them all with…
"Crucio" she whispered. A jet of light hit the boy but his body did not even flinch.
"Never used an unforgivable curse? You need to mean it! You need to really want to cause the pain- to enjoy it- I'll show you how it is done, shall I? I'll give you a lesson- Crucio!"
As the boy's screams erupted from his worthless mouth, his body trembling as if there were an earthquake only where he squirmed, she ran unopposed to his side.
"Get away from him or I swear I'll kill him!" I threatened, my wand hand shaking with indignation.
As she crouched beside him, carefully healing the first two gashes I had made in his filthy excuse for skin, she shook her head. "Y-you wouldn't. Even Sirius said-"
"Sirius?" I cackled madly, "He'll be the first one I kill after this one." I raised my wand to point directly at the gasping boy.
She shook her head again. "Bella, I know you better than anyone else- better than the Dark Lord could ever know you-"
"HA!" I shrieked, feeling my whole body begin to shake madly. "The Dark Lord has taught me spells you couldn't even begin to imagine- and I'll use them!"
She raised her head, her eyes determined, the unconfidence gone- what remained was the pure Black family- deadly beauty that made my heart skip a beat in excitement that maybe she could still come back to me- that maybe she was still me- that mini Bellatrix…
"Goodbye, Bella," she whispered softly. Her body was turning, her hand clamped to her wand, the other on his arm, about to apparate away from me forever…
"Avada Kedevra!"
The green light, the first of many to come, burst through my wand. I didn't even know which one I had been pointing at…
She was skilled. Fast. More skilled and fast than she had ever let on. In a swipe of her wand she felled a tree, collapsing it precisely in front of her, taking the killing curse for her…
When the dust from the collapsed tree settled back onto the ground, I leaped over the tree.
She was gone.
Mini Bellatrix had outdone me and left me in the same instant. I felt my whole body shake, as I let the madness take over.
-v-v-v-v-v-v-v-
"I KILLED SIRIUS BLACK!" I shrieked with delight as I ran down the Department of Mysteries, throwing spells left and right just to watch things break. I heard the footsteps after me as I turned around eagerly.
"Aww, I thought you were here to avenge my dear cousin?" I smiled as Harry Potter panted in front of me.
"I am!" he yelled. What foolhardy determination.
"Aww, did you love him, Potter?" I cooed.
"Crucio!"
As the spell hit me, I suddenly remembered… what had caused those mad laughs I could no longer suppress, what had caused me to follow the Dark Lord without any concern for the ones I had once loved? It was the one who left me. My favorite one, the only one I had truly loved. When she left something had snapped…
I screamed, then transitioned it into one of those maniacal laughs I no longer had any real control over ever since Azkaban…
"Never used an Unforgivable Curse before, have you, boy? You need to mean them Potter! You need to really want to cause pain - to enjoy it - righteous anger won't hurt me for long - I'll show you how it is done, shall I? I'll give you a lesson."
I raised my wand to point at the half blood filth, my master's hatred filling my body, my own hatred as I saw that mirror image of myself staring back, ready to leave me forever…
"Crucio!"