The only, repeat, the ONLY way this is going to happen is if she has permission from her legal guardian(s). If that means she has to get mom's permission, then she has to get mom's permission. There are no loopholes allowing her to bypass that part of the law.

Emancipation is not an option in TN, and as my friend FlyinHawk says, no state would emancipate her so that she can get married without permission.

Her other option is to wait until she is 18, when she can marry without anyone's permission.