Several reasons could be behind your health insurance company’s request for information. The first is to prove she is your wife. The company may permit spouses as dependents on the plan, but not girlfriends.
Other personal information is likely used to make sure your wife isn’t confused with another person of the same name. Next, your health insurance company needs to know if your wife has her own health insurance plan. When there are two health insurance policies in place, one serves as the primary plan and the other serves as the secondary plan. The carriers need to know about other coverage so they can coordinate benefits.
If your wife were covered by two health insurance policies, her own policy would be her primary insurance provider and your health insurance plan would be secondary coverage.
It doesn’t always make sense to carry two health insurance plans. See “Primary vs. secondary coverage when you have two health plans” to learn more.