Can SSDI and SSI benefits be decreased when the benefits are not being used to for self support?

There are some legitimate changes that could cause a reduction in your daughter’s SSI benefits.  If her SSDI benefits have increased for any reason, that may cause a reduction in the SSI benefits because the increase in SSDI benefits would be treated as additional income or assets.  At the very least you would need  to see her social security file to determine what information Social Security has that is triggering this change in her benefit amount.  You have the right to appeal any decision made by Social Security.  You will need to file a request for reconsideration, which is the first level of appeal when you get a notice of some change in your benefits.  These forms can be downloaded from the Social Security website or you can get them from your local Social Security office.

You should consider obtaining legal representation to assist you with this matter.  Interpreting Social Security rules and regulations can be confusing.  There are attorneys who specialize in Social Security matters who can assist you.