Please help

Writing this out for my SIL since she doesn’t have Reddit. Hopefully I get the details correct. In March 2021 she moved from MT to TX. She had marketplace insurance in MT prior to moving but cancelled it when she arrived in TX and got a job that provided health benefits. Unbeknownst to her, the plan kicked back in the next year (2022) and she was never made aware because she hadn’t updated her address with them. She didn’t think she needed to because she had cancelled it. When 2022 taxes were due she finds out she owes $3k for insurance she never knew she had. She has called to try to get it removed because it was obviously a mistake, and had gotten an extension on her tax filing but only has a few weeks left. Everywhere she turns she is basically told “too bad, you owe the $”. Can this really be? Can she be charged for a policy she didn’t know she had and never paid into? Who can we talk to to get this taken care of? She didn’t even live in the state providing the marketplace insurance at the time. Hope this makes sense. I can clarify any info if needed. I’m trying to help her because she’s devastated and doesn’t know what else to do anymore.