Mom may be victim of insurance fraud… advice?

My (F26) mother (F63) has had an employer-sponsored health insurance plan through Anthem BCBS for several years. Because of her income level, she also qualified for state Medicaid (Connecticut’s Husky D) for several years up until 2022. During that time, she had her employer-sponsored health insurance as her primary insurance and the state Medicaid as her secondary to cover anything left over.

That was working well until she received a letter back in 2020 from the hospital stating that state Medicaid would not cover the remaining portion of a medical bill (~$1,125) because they said they have TWO Anthem BCBS insurance plans on file – one for Connecticut (home state) and one for California. My mother and I have never lived in California.

We would have thought this was just some random error but there have been several signs that her name is linked to some California plan. When I was under the plan several years ago, a rep once had trouble finding my mother’s account because it kept popping up some California account. She also received a call recently from an Anthem agent from California. Lastly, she received some random person’s EOB for a name and address linked to California (though that paper is currently lost).

I am wondering, how likely is it that someone is committing insurance fraud against her? How could there possibly be another account with her name attached to it if she went through an employer-sponsored plan? If we call Anthem about this, can they just cover this up or deny it? Would she be compensated for the bills that she had to pay while still under CT state Medicaid? Any and all advice is appreciated.