While Allyson started the film, for lack of a better term, “normal,” at the very least the most well-adjusted of the three, she’s been changed the most by the events of the film, and she will apparently become the aggressor of the group, ready to take the fight to Michael.
The Strode women, Laurie, Karen, and Allyson have been through hell and come out the other side, but you can’t come that close to death without it affecting you, and Judy Greer recently told Total Film (via TheHorrorDude_ on Twitter) that we’ll see a very different Allyson, played by Andi Matichak, when we see her in Halloween Kills.