Had she been free to invest that money rather than pay it in payroll taxes she would have had much more than the $11,000 in Social Security she collected over eight years.
She did address the issue in the essay "The Question of Scholarships":
"It is morally defensible for those who decry publicly-funded scholarships, Social Security benefits, and unemployment insurance to turn around and accept them, Rand argued, because the government had taken money from them by force (via taxes). There’s only one catch: the recipient must regard the receipt of said benefits as restitution, not a social entitlement."
I'm not that big a Rand fan, but a person's personal behavior does not negate the value of their ideas. I think a person should exercise and eat healthy, but I don't always do it. That doesn't mean it is not a good practice.