Important!
In Chapter 4, when you play as Emma, You have to get bit while reeling in the arm slide. Reel in slow at first, then the second time, reel in fast. The werewolf (Max) will notice you are up there and start walking towards you. You will then have the option to jump or finish reeling in the slide. Choose the latter, then you will be bit in the arm and now Emma is infected.
Now later down in the chapters, Emma will be hiding in the car and Jacob will be caught by the old man leaving him inside a cage in the Hackett basement. As Kaitlyn, just shoot werewolf Emma with regular bullets to scare her off, and as Ryan release the cage for Jacob to escape.
You have to kill Chris Hackett as Ryan when you fall back down to the Hackett household. That will cure Max and in turn, cure Emma. Later in Chapter 10 when Jacob runs into a distraught Emma in the forest, Choose to fully admit it was all his doing for this whole ordeal.