Read this part already know she stole the money and tried to use missing bag as a cover up

The staff know that the till sure got cctv, so cannot escape from the fact that she took the money. Maybe she got reason to take money, like take to buy something for the company or to bank in as cash, etc.

However she want the money for herself. So she pretend to lose her bag, so that the money can be "stolen".

She thought that by doing this way, the suspicion won't fall on her but maybe on the guard or something that "stole them money".

She doesn't realize that even if she legitimately took the money, she is responsible for it. If its lost during her possession, then she has to pay it back.