With out knowing her past it's hard to say what's going on in that brain of hers. Just keep helping her for now and hopefully she'll grow out of them.
I know King didn't have a happy past and it took over a year for his REALLY bad dreams to go away (mostly... there was always that occasional one.)
Do you keep your place too warm at night? 19.5 - 20.5 C is usually about right for sleeping (for humans) 21 C is too warm though. Being too warm can cause bad dreams. I have no idea what proper sleeping temp is for dogs but i still imagine it would affect them.
Maybe let her sleep with a shirt you wore that day?
Let nature guide your actions and you will never have to worry if you did the right thing. ~ crow_noir
The pet world excels where the human world is lacking; sterilization and adoption. ~ crow_noir
Please, if your dog is arthritic look into getting it Elk Velvet Antler. Look up my posts on it, PM me, or look it up on a search engine; but please if you love your dog and want it to live many more years consider this option. I've seen so many posts on here about dogs needlessly suffering. I can't make a new post about EVA every time so this plea is going here. EVA also helps with other ailments such as anemia.