SSI benefits and retirement of mother

You should seek one-on-one counseling for your situation.

To be eligible for SSI you must be :
* Aged (65 or older), blind, or disabled.
* Have limited income and resources (assets)
* Be a US citizen or qualified alien

The status of one's parent's is not a specific factor (ex. is parent retired), but income or assets received from a parent may be a factor. However, in general, deemed income from a parent stops the month after a child turns age 18.
For example, a child who could not receive SSI because of deeming may be able to get SSI when he or she turns age 18.

http://www.ssa.gov/ssi/spotlights/spot-deeming.htm