How much sleep is too much when recovering from a hospitalization?

Cekc45 asked...

My grandmother was hospitalized at the beginning of January with bronchitis. After spending a week in the hospital, she was allowed to come back home and now is fully recovered health-wise. However, her energy level seems to be cut in half from what it was from before the hospital stay. She will sleep until 8:00 AM, get up for the morning, and then go down for a nap after lunch that takes up the whole afternoon, get up for dinner, and then go back to bed so she's in bed by 7:00 PM. She's really only up and moving around for about 4 - 5 hours a day. Is this normal? She's 90-years-old and I don't want to push her but am wondering how much a 90-year-old should be sleeping? Should she be up and doing stuff more? How can I motivate her to spend more time up and moving around? I've tried activities like puzzles, crossword puzzles, etc. but she does not use them. What other activities can she do to keep her busy? And how much time each day should she realistically spend sleeping?