1. She must have less than $4700 of taxable income. Disability may or may not be taxable, depending on who is paying it.
2. You must pay more than half her total support. Remember that even if the disability and social security are not taxable, they count as support she provides herself. You need to add up the value of all the support she receives and determine if you paid more than half. There is a worksheet in publication 501 that can help with this. Support includes a portion of your home rent, utilities and food, plus her costs for entertainment, medical, etc. https://www.irs.gov/pub/irs-pdf/p501.pdf
3. She can't file a joint return with a spouse, except in special circumstances. If she is married, she will generally have to file married filing separately, as will her spouse.
4. For a parent, she does not have to live with you. But if she does live with you, part of your household costs count as support provided by you to her.
