One or both of them, your wife and/or her mother, are borrowers on the loans. It is possible that they are co-borrowers, or for one to be the borrower and the other a co-signer.
There may be an effort within the loan contract to impose a choice of law provision that extends to the statute of limitations. If so, it would be necessary to review that language to determine what state's law it attempts to impose, and whether the provision is likely to be enforced by a court.Quoting Kash0509
Otherwise, as statutes of limitation are normally regarded as procedural laws, the statute of limitations that is applied will be that of the forum -- the state in which the lawsuit is filed -- unless that state has a borrowing statute that applies the out-of-state limitations period to the loan. Last I checked, Georgia did not have a borrowing statute.
Georgia's limitations period for written contracts is six years. Depending upon the full facts, that period may have started to run as late as October 2015 (the date of the missed payment, with there apparently being no subsequent payment), or possibly and earlier date.
Tolling provisions potentially extend the statute of limitations. If a state provides that some or all of the period of time you were out of the state after a claim accrues is not counted toward the limitations period, then the statute will toll the limitations period for that amount of time.

