You're exactly right. My older son is on the spectrum. The very first thing we did was get him a service dog. We now know that what the dog does is trigger oxytocin. Oxytocin shuts down the stress response.
The problem with PTSD is that the victim has what's called a kindled or heightened stress reactivity, so all kinds of things send them into hyperarousal. It's not just a simple fix—“Let's go get a Lab”—although, as the owner of a Lab, I can attest to their incredible benefits for calming an autistic kid. There are all kinds of ways. It's really a case that, for these women and kids, we want to give them as many different ways of triggering the oxytocin as we possibly can.
It's a great question.