Welcome to Spark People ! I'm sorry to hear about your mom. Don't beat yourself up because you turned to food for comfort. That's something that has happened to every single member of SP at one time or another. Eating too much one day does not make you a bad person or an unhealthy one. With time, you can learn to manage your stress more effectively. but that does take time.
Does your mom have a computer ? Can she SKYPE ? even though you're 2300 miles away, you can always use SKYPE to stay in touch or you can even talk on the phone. it's a way to stay connected when you're far from the person you love.
I know having a diagnosis of cancer is never and easy thing, but people are surviving and thriving today. One thing you might do is check your area for local cancer support groups. A support group can help you get through those rough times when you're not with your mom.
You could even join one of the many Spark cancer teams. You might want to check this one out. www.sparkpeople.com/myspark/groups_individ
With time, you will learn to manage your stress. Try reading some of the great Spark articles on stress management. they can help too. www.sparkpeople.com/myspark/groups_individ