I don't know anything about the AU. All I know is that Cream dies and Vanilla loses her shit on Tails. So, this will be my take, I guess.

You're Vanilla the Rabbit. Your daughter is Cream the Rabbit. You raised Cream alone. You live on Mobius. You're friends with the Resistance and part of it. You're a self-trained fighter, but also getting trained by Knuckles and Shadow. You can be badass and scary sometimes. Tails has gone mad, but not the normal kind, the calm, cold, emotionless kind. He's already killed Big and Blaze. The Resistance, especially Sonic, is angry, terrified, and worried for what will happen next. You've been defending Cream as best you can, even at the cost of yourself. Gemerl has been reprogrammed to act as a guard and caretaker for you and Cream. Everyone is always one bad day from a mental break.

You're standing in a dull, dead, grassy field in Green Hill. Your ears, fur, and flows flowing in the wind. The Resistance is with you. Cream standing in front of you, running to you. You were just about to leave, from dealing with Tails' badniks. Suddenly, you hear and see a gunshot. Not at you, at Cream. The bullet hits her right in the heart, making her drop dead instantly. Her blood spattering your clothes and face. The Resistance look shocked, pissed, and terrified. Tails is in front of all you, standing there with a smoking pistol. He looks calm, calculating, and cold, as usual. Not you, though. You just watched your only child, your entire world, your little girl, drop dead in front of you. You've already snapped, but you can't do anything. All you can do is scream, cry, wail, whimper, yell, and stay angry. Shadow's the same as you, but not crying, PISSED. He saw Cream as a daughter, reminded him of Maria, and now Cream's gone, too. He takes his Inhibitor Rings and lets them drop to the ground, releasing his full power

Tails: Pathetic.

Shadow: YOU FUCKING MONSTER!!!