Honestly, nothing you describe would worry me very much. She's an old girl with some quirks. The futzing around with her bed only to abandon it is pretty cute when you tell it (though, I imagine it's a little annoying at 2am).
15.5yo is awesome! What breed/sort of breeds is she? Our eldest is a 13.5yo dachshund- he's a funny old grump!
It doesn't sound like it to me. Older dogs are quirky. By the time our boy was 18, we had like 10 beds on the first floor for him because he would try and drag them into whatever room we were in.
Sounds like old dog behavior to me too. They are quirky and I think it is just harder for them to get comfortable. I mean I am only forty and sometimes I have to fluff and rearrange my bed to get comfortable. ;-)
"He is your friend, your partner, your defender, your dog. You are his life, his love, his leader. He will be yours, faithful and true, to the last beat of his heart. You owe it to him to be worthy of such devotion." - Unknown