Have you tried her without any dorm or other tranq? Is it possible she won’t settle down because she’s fighting it?
I’ve had some (WBs, if that matters) jump out when they were first turned out (I’m not sure if they were in their previous barns or what their set up was), but we caught them and put them out again (and eventually the barn built higher fences and hot wire). We did not have large pastures so they were in smallish paddocks – it doesn’t make it harder for them to injure themselves or jump out, which they can do it from a stand still if properly motivated (heck, I’ve even seen a pony leap out of a stall that only had bottom door). The TBs stayed put, but none were fresh off the track.
I had another horse who was used to turn out, but mostly in a small space. When he got to new owner who had like 20 or so acres just for the horses, he ran and ran and ran and ran for the first day (and was out with several others who were unimpressed by his antics). He was VERY body sore the second day, but was fine after 2 or 3 days (still outside for at least 12 hours) and hasn’t repeated that spree again. I would agree with everyone saying that sometimes you have to let them figure it out on their own.