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The problem here is that pay is not a legally guaranteed amount in most cases. Without a contract specifically stating what your pay should be, an employer is permitted to legally pay different people at different rates, unless it can be shown that the employer is discriminating based on race, religion, gender, age, disability or FMA use.
This is not the sort of job that would be subject to any "prevailing rate" laws, so if they are paying her what they said they would be paying her, there really isn't anything to be done aside from alleging discrimination
(if she can show other starting pharmacy techs that received a higher rate in close temporal proximity to her hire date).
This would be an entirely different situation if she had not already been aware of the seemingly low rate at the time of hire. If they had promised a higher rate and then, after she started, tried to explain that a mistake was made about the offered rate, we'd have some implied covenant concepts to work with here.
The facts you've given though just don't support that legal theory.