Can HIP cancel my MIL's insurance in the middle of an illness?

Did MIL get on Medicare & Medicaid recently? Sometimes an insurer will not pay once that happens as Medicare is the first source of payment for hospital and physicians fees, etc with Medicaid paying for everything that Medicare doesn't cover. Sometime when this happens, the insurer can do a clawback for all payments made to providers from the time of Medicaid eligibility and will repay the premiums from the month that Medicaid started. Could this be what happened?

HIP is the Health Insurance Plan, a very large private health care provider in NY.

Does HIP mean Health Insurance Provider? I know that MIL means Mother In Law but haven't seen HIP before.