I agree that depending on what state they live in will be a determining factor, but I also strongly disagree about "guidelines of income as to who has the best ability to financially care of the children..."
The Child Support Guidelines are recognized nationally by every state and they are clear as to NOT being a determining factor in custody issues ever! Custody is determined strictly on the best interests of the children... in any state period.
She should give me a call 1-800-DIVORCE