It would make no sense for the manager of the store to hire Chelsea at all. For one, Raven obviously did a much better job on the application and on the tests, this could easily strike suspicion and trigger an investigation were it anybody else, which did happen but might not have if not for Raven's vision. Secondly, Chelsea had no idea what she was doing. So this manager decided to pay a girl to do a job which she simply can't do at all? Even if this was simply out of spite, a higher authority could have found out that she had a completely incompetent employee in her store causing big trouble for her. Either way, it's clear the writers should have made Chelsea able to do her job well, and make Raven have her vision so Chelsea's still able to get the confession from the manager and it would make a lot more sense for Chelsea to be hired.