Hello and thanks for the query.
Sleep needs change over a person's lifetime. Children and adolescents need more sleep than adults. Interestingly, older adults need about the same amount of sleep as younger adults -- seven to nine hours of sleep per night but they don't get it in one block.

 Older people often sleep less deeply and wake up more often throughout the night, which may be why they may nap more often during the daytime.

There are many possible explanations for these changes. Older adults may produce and secrete less melatonin, the hormone that promotes sleep. They may also be more sensitive to -- and may awaken because of -- changes in their environment, such as noise.

Older adults may also have other medical and psychiatric problems that can affect their nighttime sleep. 

Not sleeping well can lead to a number of problems. Older adults who have poor nighttime sleep are more likely to have a depressed mood, attention and memory problems, excessive daytime sleepiness, more nighttime falls, and use more over-the-counter or prescription sleep aids. Poor sleep is also associated with a poorer quality of life.

Many people believe that poor sleep is a normal part of aging, but it is not. In fact, many healthy older adults report few or no sleep problems. Sleep patterns change as we age, but disturbed sleep and waking up tired every day are not part of normal aging. If you are having trouble sleeping, see your doctor or a sleep specialist. There are treatments that can help. 

If your grandmother has no problem after getting up in the morning and doesn't feel tired or have any depression,then it is normal and should not be worried upon.

I hope to have answered your query however you may revert to me for any further query.
Best of luck
Thanks

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