How To Lower Blood Sugar Levels?

I took my daughter with me to "Life Line Screening" . She is 44, weight 303, and her blood sugar was 300. She does not have insurance. If she starts eating properly the healthy way will this bring the 300# down. This really scared her so I know she is choosing the right foods to eat now. Also, she cannot sleep at night even with taking something for sleep. She needs sleep. This has been going on for at least a month.
Thank you for your assistance,
Linda Smith