回复：签证官在I94表上写错了，我们怎么办？

Technically, that is not a mistake, because the immigration officer can write down any expiration date he/she sees fit. Anyone should check their I-94 date before leaving the immigration restrict area within POE and ask for a reconsideration if you think it's too short for the purpose of this stay.
You should call your local CIS office and see if they have in-house customs border officers? (some CIS stations only have CIS officers and no ICE/CBP officers)
Or call your nearest international airport customs/immigration office.
Or you can always file for an extension.
But technically, she is out-of-status now by doing nothing before the expiration.