No, a Court Order is not needed when filing a Final Return for your mother-in-law in this case.
Be sure you indicated in the MY INFO section that the taxpayer is deceased and check the box that 'you are preparing this return for a deceased person'.
When there is no executor or administrator, whoever is responsible for filing the return should sign the return and note that they are signing "on behalf of the decedent."
TurboTax will complete Form 1310 for you if a Refund is due. You won't need Form 56.
Here's more info on Death in the Family.
Sorry for your loss.
@BruceBShiba
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