Sister lives with me and pays $400/month for lodging which includes utilities, internet, garbage service. Lodging expenses per month are between $2300-2400. Dependent?

No.  If she is paying you to help out with expenses, she would not be your dependent.  In order to claim your sister as a dependent, you would have to provide over half of her support for the year and she would have to less than $4,700 in income for the year. 

To claim someone as a Qualifying Relative, they must be:

• Your child ( including step children, adoptive children and foster children) or a descendent of them
• Your sibling (including half siblings) or a child of your sibling or a sibling-in-law
• Your parent or grandparents, including step parents and in laws
• Any other person that lived with you for the entire tax year
• Not a qualifying child of another taxpayer
• Someone that you provided over half of their support for during the tax year
• Has less than $4,700 in income (not counting social security)

You have a family cost sharing arrangement---which is not entered anywhere on a tax return.