@Sweetpea have you tried asking your daughter what would make her feel safe? That is, what is different about where she is now, your house and any other potential place she might live that causes her anxiety.
I understand you aren’t likely to get practical answers or she may not want to reveal details of her fears if you are part of them, but it may help to try and pinpoint what her fears are. For example when I had a psychotic break, I chose to go to the hospital instead of home with a parent. At the time, I believed the parent had died and been replaced by an impostor and even if the parent was real, I may have been harmed by the parent in the past. While in the hospital for a few days, these concerns faded as I had other pressing issues and goals.
While I generally don’t suggest caregivers to baby their adult children, you may want to look at this in a similar fashion as a child who is afraid of ‘monsters’. I don’t recommend any suggestion that her fears don’t exist, rather you may stumble on some equally superstitious or illogical way to make her feel safe. I’m thinking of the old joke about the charm/necklace that keeps polar bears away that’s been 100% effective so far. It might be something simple like installing a lock or a simple burglar alarm, or may be not.
I guess this is an practical extension of the LEAP method, so you may want to search and read up on this on the forum and elsewhere.