One of our employees stole money from our deposit by closing the books early and stating that she already dropped the money in the safe. The Owner checked the safe (he's the only one with the key) and none of the money she said she put in there was present. Then we discovered that all the petty cash was stolen after we closed the office. This person had keys. Ultimately, she stated that she was going into rehab so I requested that while she's gone we do need her keys back. She then asked for her final check. I told her that she must discuss that with the Owner as we haven't fired her. Please advise if we are legally allowed to withhold the money she stole from her final paycheck. Thank you so much for your time and assistance.