To start with, get her a litter tray if you haven't already - as the other answer has said, she's afraid to go outside. It's going to take time for her to be comfortable going outside again after a major scare like that.
The first thing you want to do is provide her with a safe (dog-free) space outside. If you can't keep the neighborhood dogs out of your yard, I'd suggest you build her some kind of cat habitat - it doesn't need to be fancy, just something where she can come and go at her own rate where dogs can't touch her. Chicken wire secured with stakes is ugly, but works. So does a kitty tunnel to a greenhouse or screened in pavilion (or anything else that's fenced/screened so dogs can't get in)
Once you have the safe space, I'd suggest you start by enticing her out with treats, and being there when she's outside, so she associates outside with good things. Once she's going outside on her own again, if she doesn't start doing her business outdoors, the next stage is to progressively move the litter box closer to the kitty door.
Once it's at the door, wait a few days before moving it outside the door (cats are notoriously change-averse), and make sure she knows that's where it is. I strongly recommend picking a time when it's forecast to be fine for a few days when you take this step, because you could end up spending quite a while enticing her to her litter or need to leave the box outside for a while. If you don't have a sheltered spot outside the kitty door, you want to make sure you've got a covered box because rained on kitty litter is nasty.