Yes.

A person can still be a Qualifying relative 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)

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.