Social security isn't included in her gross income calculation, I don't know why they would tell you that. It sounds like you provide for more than half of her support.
If you haven't already looked at Publication 501 by the IRS, here's the link:
http://www.irs.gov/publications/p501/ar02.html
http://www.irs.gov/publications/p501/ar02.html#d0e3763
Another reference:
http://www.usatoday.com/money/perfi/taxes/2007-03-09-aicpa20-scutellar o_N.htm



