I didn't even have any pain medication for those months. It wasn't until I had an MRI (because I was whining so much to my doctor) that he discovered the tear and bone spurs. Sleeping was not so great, but once I got it repaired and didn't have to sleep with the sling on any more (I had to do that for about two weeks after surgery), I slept like a baby.
Is her's frozen? I didn't have a frozen shoulder, so I was lucky about that.
Make sure she gets the pain pouch. It lasts about two days and I took two pain pills after surgery and that was all I took. Mine was done as an outpatient and I slept in a chair for the first two nights after surgery until it was just too uncomfortable and I was tired. I never really had much pain at all, even during physical therapy afterwards.
I slept on my side, with the pillow under my arm with my arm resting on the pillow. I didn't sleep on my other side (lying on the bad shoulder) for nearly five or six months before.