Final answer:
Blue Cross Blue Shield is billed first as the primary insurer for Sheila's daughter's well-child exam, and Medicaid may cover any remaining costs as the secondary insurer.
Step-by-step explanation:
When a patient has multiple health insurance coverages, there is a coordination of benefits to determine which insurer pays first. In the case of Sheila's daughter, who is covered by both a commercial insurance plan, Blue-Cross Blue-Shield, and Medicaid due to low-income status, the primary insurer is typically the commercial insurance, in this case, Blue-Cross Blue-Shield. Therefore, Blue-Cross Blue-Shield is billed first for the well-child exam. If there are any costs not covered by Blue Cross Blue Shield, Medicaid would then be billed as the secondary insurance. This process ensures that Medicaid, which is intended to serve as a safety net for those with low incomes, acts as the payer of last resort.