I suggest you review the interview for your mother-in-law to confirm that she is a dependent.
You can see this in the My Info (Online) or Personal Info in (Desktop)
Your mother-in-law may be eligible as Qualifying Relatives.
"A qualifying relative must meet general rules for dependents and pass these tests:
Please see the IRS publication Dependents for more details.
Provided they meet these guidelines, you can claim them as dependents.
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