Only if she lived with you all year. Even then you would have to meet the other dependent rules, primarily that you provided more than half her support.
A person can still be a standard dependent, if not a Qualifying Child, if he meets the 6 tests for
claiming a dependent:
1. Closely Related OR live
with the taxpayer ALL year
2. His/her gross taxable income for the year must be less than $4,050 (2016-17)
3. The taxpayer must have
provided more than 1/2 his support
4. He must be a US citizen or resident of the US, Canada
or Mexico
5. He must not file a joint
return with his spouse or be claiming a dependent of his own
6. He must not be the
qualifying child of another taxpayer
Social security doesn't count
as income, for the income test, but social security money he/she spends on her
self does count as support not provided by you, for the support test. Money she
puts into savings & investment does not count as support she spent on
herself. If no one person
(or married couple) provides 50% of the support (for example her siblings are
also sending support), then a "multiple support agreement” (IRS Form 2120)
can be used, to allow you to claim the dependent. https://www.irs.gov/pub/irs-pdf/f2120.pdf
The IRS has a
worksheet that can be used to help with the support calculation. See: http://apps.irs.gov/app/vita/content/globalmedia/teacher/worksheet_for_determining_support_4012.pdf
