She files a 2016 Form 13010 regardless of filing date.
Form 1310 is part of your father in law's last personal tax return. It is not part of the estate returns.
Since he was alive in 2016, a final Form 1040 needs to be filed on his behalf. You wife will complete form 1310 to claim any refund from the tax return. You do not need to wait until the estate is settled to complete this final tax return.
For more information about filing taxes for deceased persons, follow this link: IRS
on Deceased Taxpayer
