Lack of sleep can make you feel tiredness. There are multiple causes for insomnia to occur such as anxiety, any underlying medical condition such as arthritis, etc. , psychological causes and substance abuse. I would advise you to meet a psychiatrist so that she can be examined and undergo the necessary investigations to find the underlying cause of the problem and have it treated accordingly. Kindly don't worry about any social stigma by going to psychiatrist just keep in mind that mental health is just as important as physical health and the underlying cause should be found and treated.