My question involves name change laws in the State of: I am not sure if it would be from TX or TN...

My divorce was finalized in Florida, but the most recent child custody agreement is on file in TN which is where the father still resides. The child and I have lived in TX since 2006. I am not sure which state this question would apply to since we have an interstate case.

My question is this:
My daughter will turn 18 on July 21 and wants to change her last name from her dads name to my maiden name as she has nothing to do with her dad. She won't speak to him when he calls and has not seen him in 3 years or more.
If she changes her name to no longer reflect his, does that change is obligation to pay the the 7500.00 he still owes in back child supprt?

Thank you