Yes the stimulus payment is actually an advance for a credit claimed on a 2020 tax return filed in early 2021. You can claim the credit when you file your 2020 tax return. 

But in order to qualify for the credit on the 2020 tax return, she still needs to update her Social Security Card/Number that is valid for employment.

Have you asked if they are able to update her card with a face-to-face appointment, so you don't need to mail her documents?  If you do need to mail her documents, you may consider Registered Mail.

No face to face appointments in San Jose at the moment, but hopefully they will open again before 4/15/2021

Were on the 2020 will I enter for this credit

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@JVM1 wrote:

Were on the 2020 will I enter for this credit

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The TurboTax program will ask you about any stimulus payment after you complete the Other Tax Situations section.

you will see the credit on line 30 for Form 1040, but with out clearing that flag, it will remain a problem

The form that occurs 'behind the scenes' requires a 'valid social security number; and that is defined in the Form 1040 instructions as 

Valid social security number. A valid social security number is one that is valid for employment in the United States and is issued before the due date of your 2020 return (including extensions).

So seems like you have to clear up the issue prior to April 15 or request an extension to Oct so that you are eligible for the stimulus.

https://www.irs.gov/pub/irs-dft/i1040gi--dft.pdf

see page 56 of the instructions (look at the right most column for the definition I posted above)