My suggestion is to first determine if the aging parent needs to file a tax return.
Use the IRS conversation at https://www.irs.gov/help/ita/do-i-need-to-file-a-tax-return
Click the "Begin" button at the bottom of the page and enter their information.
The result will tell you if they needs to file.
You can also refer to https://www.irs.gov/publications/p501#en_US_2021_publink[phone number removed]
In this link, it is addressed under "Who Must File."
Also https://www.irs.gov/taxtopics/tc553 addresses some more unusual situations regarding a dependent's unearned income.
This will address if they need to file.
If they do not need to file, then determine if you can claim her as a dependent.
Follow the instructions at https://www.irs.gov/help/ita/whom-may-i-claim-as-a-dependent
If both options are possible, the only way to tell which is "better" is to go through the process of calculating the taxes both ways and determine which way results in the least overall taxes.
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