If her blood sugar is too low, eating carbs will raise it back up. If her blood sugar is consistently too low, she might need an adjustment in her insulin doses. She might need to call her dr office and make an appointment to see them earlier if this is the case. Different things happen to different people when they sleep. Sometimes because they dont eat for a long time their glucose gets low during the night. In this case, it is beneficial to have a snack before bed. A good snack in this case is some carbohydrate along with some protien and a little fat, like maybe a piece of toast with peanut butter on it. Some people have something called "liver dumping" where the liver releases glucose early in the morning and they wake up high. So its hard to tell what is happening with your mother without knowing what her blood sugar readings are.