OP- please be aware that “changing their dependency” is not a simple matter of a kid declaring “I’m no longer a dependent.”
“By law, to be considered independent on the FAFSA without meeting the age requirement, an associate or bachelor’s student must be at least one of the following: married; a U.S. veteran; in active duty military service other than training purposes; an emancipated minor; a recently homeless youth or self-supporting and at risk for homelessness; a parent who provides more than half of the financial support for a child who lives with him or her; or someone who has been in foster care, been an orphan or a dependent or ward of the court for any period of time after the age of 13.”
I’m not sure OP wants his/her kid to be homeless (or at risk of homelessness) in order to get more aid. Or any of the other situations…