"Andy, Cissy!" Bellatrix cried, her younger sisters were tearing up as they watched. The eldest girl had spoken out of turn to their father, he, already having a bad day, used one of the worst curses on her. The cruciatus curse, and being the cruel man he is, he made the younger girls watch.
This went on for an hour straight, all three children sobbing and Cygnus standing there, flicking his wand. They couldn't sleep that night, staying up and comforting eachother.
"Bella, promise that you'll never leave us, no matter what"
"Of course, Cissy, I promise"
"Let's make a pact."
Each of the sisters cut the palm of their hands with a piece of glass.
Now they surely could never leave eachother.
-----
"Bella, think about this!" Andromeda begged, crying for her older sister to stop. "Maybe this will make you think about your decision to marry this filthy mudblood, ANDY!" Bellatrix screamed, cackling like a mad woman. Andromeda drew her wand at her sister, the deatheater's eyes widened. "TAKE THE CURSE OFF OF MY HUSBAND AT ONCE, BELLATRIX" she screamed, tears flowing out of her eyes, as said husband writhed in pain under Bellatrix's curse.
"Andy-"
"YOU HAVE NO RIGHT TO THAT NAME ANYMORE"
Bellatrix released the curse, bewildered at the statement. "Please, I'm sorry, I just- I don't want you ruin the family line with DIRTY BLOOD!" She screamed.
"BELLATRIX YOU ARE BRAINWASHED."
"YOU ARE THE BRAINWASHED ONE, ANDROMEDA"
Andromeda scoffed, "You are no longer the Bellatrix Black I knew. You've changed, your mind is weaker. You are now Bellatrix Lestrange, Bellatrix Black is dead, and you know it"
Bellatrix let out a weak excuse for a laugh and aparated back to the Lestrange mansion.
-----
"Andy please. I don't want to do this, you're my big sister and I'd hate to hurt you, mum and dad will crucio me if I don't come back with you or Theodore Tonks' dead body."
"I'm sorry, Narcissa. The Black family's beliefs are long behind me, I'll marry who I wish. Bellatrix has gone off the deep end, but I can still save you, just leave the family and come with me" Andromeda attempted to reason with her sister, but Narcissa wouldn't listen. She was dead-set on her beliefs, and she couldn't care less what anyone had to say about it.
"Andy. I promise, you don't want to marry a mudblood, they're tainted and dirty, if you would just just listen to me-"
"I have listened for twenty years, Narcissa. I'm finished listening. I want you to hear ME!" The middle child yelled at her younger sister.
------
"Cissy, why would you lie to him?!"
"I needed to know that my son was safe, Bella, it had to be done."
"YOU AREN'T LISTENING. HE'S GOING TO PUNISH US BOTH NOW, ALL FOR THE BRAT TO BE DEEMED "SAFE"? HE CAN STILL DIE. HE ISN'T INVINCIBLE AFTER HARRY POTTER SAYS SO"
"Bellatrix."
"Cissy"
"I love you to death, and I always will, you know that?"
Bellatrix's eyes widened, welling up with tears, she had no response. Narcissa walked up and held her elder sister tight in her arms.
"Thank you for never leaving me"
Those were the last words Narcissa spoke to Bellatrix.
------
Informing Andromeda probably hurt the worst, though. They hadn't seen her since she was disowned in 1971. Narcissa cried with her elder sister for hours. Bellatrix had died of her own arrogance, underestimating her opponent.
They new that there was no saving her, but it still hurt. She was all Narcissa had left, divorced from Lucius and her son on probation at Hogwarts.
Andromeda wished her last words to her sister weren't anger. She wished she could go back and apologize. She wished she could go back and say "I love you" one more time.
-------
Bellatrix, in the afterlife, wished she had said "I love you" more. She wished she didn't go insane. She wished she had cared more.
But there is no changing the past.