These websites could be somewhat useful.
http://www.georgiachildcustody.com/
http://www.divorcelawinfo.com/states/ga/gacustody.htm
Be advised, every situation is different.
The biggest wildcard is the judge.
Bottom line, most judges place little if any weight on a child's preference.
Why?
Children are legal incompetents.
Courts are not required to even acknowledge their presence.
Some judges do, more judges don't.
Even when the child is allowed to express their wishes, that's all they are, wishes; as opposed to rights!
Proserpina is about as spot on as it gets in your case.
You might wish to consult an attorney.
Most attorneys will meet with you for free and do an initial consult and assessment. You could seek clarification on how much your local judges value a teenagers input.