Dear Concern,
Here, the first question is since how long your wife is working with that organization? This is very important question, as all the benefits for which she may be entitled are based on service length. Second thing, how she was communicated for putting resignation?
The above comments from respected members have must clear the picture in your mind, but still I want to clear few things.
As Dinesh Ji has well said, she need not revert to the organization's communication for resignation, as she will cease all her benefits from the date of resignation, including maternity benefits. So, it is better to keep quite and let the company process at its own.
As the company is shutting down, they need not any resignation but, if they will settle the Full & Final Account of an employee, they will have to settle his / her all legal dues as per land of law and in terms of the employee's Appointment Letter too.
So, in my view, she need not to give the resignation at her own.