I don't agree that there is an age to stop Trick or Treating but there is a general knowledge that when a child doesn't want to go anymore, then you stop taking them, especially when they hit the age that it is inappropriate to go.
For Abbie, there is probably a few Fall Festivals or Halloween parties, for ID and/or Autism kids to go too. Heck, Selfish World is even putting one on. Dress up not needed, come dressed if you want, but festive wear is usually always welcome, especially for kids with sensory issues. I know of 4 parties in my area even and have 2 marked on my calendar. We will not be going door-to-door, I have 2 in costumes and 2 dressed in holiday wear.
She seriously needs people that will respect her sensory issues and needs..