Why does Khala Jamila do when the General is in the hospital, and why does she do it?

She is a nurturing person to him, It is her duty. Here is a quote,

"What I remember most about the general’s hospital stay is how Khala Jamila would wait until he fell asleep, and then sing to him, songs I remembered from Kabul, playing on Baba’s scratchy old transistor radio."