Final answer:
The nurse should refuse to provide the test results to the insurance company representative due to patient privacy rights.
Step-by-step explanation:
The nurse's best response to the insurance company representative requesting the test results of the child's genetic abnormalities would be to refuse to provide the information. This is because the test results are confidential and should only be shared with the parents and the child's healthcare provider. Sharing the results with the insurance company without the parents' consent would be a violation of the patient's privacy rights.