My 15 year-old dog paces in circles when it's almost time for his pain pill and I think it's because his pill is wearing off and the returning pain makes him anxious. I was only giving him the pain pills when I could see him acting stiff but his quality of life definitely improved once I started giving them to him regularly, so maybe your friend should ask her vet for a low dose pain pill or a recommendation for treatment/course of action.
For me, his decline was over many months and I just kept rationalizing that it was normal aging but I saw a marked improvement in his activity level and demeanor once his pain/discomfort was addressed on a regular basis. My little guy also has poor eyesight and is hard of hearing and, as
@bisousx says, I think it's frightening and disorienting for them and the pain pill has a bit of a calming effect as well as pain relief. I'd much rather give him the pill twice daily, even if he doesn't really need it, than have him suffer without it because I misinterpret how he's feeling.
He was barking happily this morning when I made pancakes, he eats with great gusto and he still runs around and plays with us and his furry brother. I give a lot of the credit to his medical treatment. I know he doesn't have a lot of time left but lessening his pain means his last few weeks or months will be at a high quality of life and that's everything I can hope for.