she put that on your passport?? That is totally wrong and should have been reported to the airline Ground Security Coordinator and the screener's supervisor. Are you sure it was marked on your actual passport?

The 'SSS' is the secret code which indicates you need a secondary inspection - if she pulled you out of line, then you were either 'SPOTted' (deemed suspicious) or she didn't like you for some reason.

'SSSS' is usually issued on the BP automatically by the airline if you meet certain selection criteria (one way ticket, pay with cash, etc.) - those are hard to remove.

If a screener every writes SSSS or marks your bp for secondary and another checkpoint is available to you in the terminal, just leave the line, go back to the airline to get a new BP (use the kiosk or tell the agent you lost the bp) and go to a new checkpoint.