There are two different types of "drug evaluations." Most often the court orders drug testing to screen for drugs in a person's system. This is usually a urine test. Occasionally, and this would only after a person tests dirty for a drug test, the court would order a substance abuse evaluation. This would be done by a trained professional to determine if someone had a substance abuse problem.
If a person was ordered to take a drug evaluation and does not submit it to the court it is as though she did not take it. Typically, drug evaluations are used when custody is at issue. If you are referring to a drug test, if she does not submit the results of the drug test to the court, the court will treat the test as though it is dirty. If you are referring to a substance abuse evaluation, which is usually done to determine whether the current orders should change, if the results of the evaluation are not submitted to the court, the court will not make any changes to the orders until a satisfactory evaluation has been submitted. If you believe that the results of the evaluation are incriminating, you should subpoena the information directly from the source and submit them to the court yourself.