The Girl (final)

Chapter: 8 · Water Treatment Plant
Where: Water Treatment Plant: Sedimentation, Storage Area, Chemical Treatment and Control Room (1F); the Loading Bay (2F), under the roof hatch.

Weak point

Light: floodlights stun her (about 15 seconds, one use each) and sunlight from the roof hatch kills her.

The last encounter with The Girl and the only one where she dies. You have to restart the 3 Power Distribution Units to open the roof hatch while she roams 1F. Your tools: the floodlights, the Molotov Cocktail (freezes her), the Empty Bottle (distracts her) and the Requiem (1 round stuns her on Casual and Standard).

Keep a Requiem round for the Control Room: it's the best spot for Bring Out the Big Guns.

Reward

The way to Emily. Bring Out the Big Guns (200 CP) if you stun her with the Requiem.

No published HP. Supplies for this fight: 12.7x55mm Ammo ×1 (Sedimentation northeast container), ×1 (Storage Area southwest barrel) and the Molotov Cocktail in Chemical Treatment, on every mode; a Med Injector in the Chemical Treatment northwest barrels (not on Standard (Classic)). Insanity: it takes 2-3 Requiem headshots or 2 Molotovs to stun her. Two versions of the finish: Game8 and KeenGamer say to shoot her with the pistol; PCGamesN and FinalBoss say the sunlight finishes her. Both work.

Step by step

Roof Hatch Controls: press the switch. The hatch doesn't open, but the 3 units get marked on the map. Go down to 1F.
Sedimentation: she screeches and roams. At the three-way split she appears ahead: back off or throw an Empty Bottle far away.
Unit 1, Storage Area (the easiest: do it first). She knocks barrels over and blocks the lever. Switch on the nearby floodlight to stun her, slip past and pull the lever.
Unit 2, Control Room: its lever is missing. Take the Crank Lever from the shelves of the adjoining Filing Room. She bursts in and throws Grace away from the console: 1 Requiem round (trophy), or lure her into the Filing Room or a lit room, loop back and fit the crank.
Unit 3, Chemical Treatment: the lever is jammed and needs holding for about 10 seconds. She drops from the ceiling vent as soon as you touch it. Throw the Molotov Cocktail from the metal trolley by the lever to freeze her and hold A. Alternatively, lure her to the floodlight on the other side of the window and loop around to the right.
Loading Bay (2F): ride the lift back up. She attacks by the hatch: switch on the floodlight aimed at the hatch switch to freeze her and open the Roof Hatch. The sunlight melts her.
A prompt to shoot appears: finish her with the pistol and keep the Requiem.