Can the state go after me for funds from my mother-in-law made before nursing home

My husband recently passed without a will. Additionally, he never updated the beneficiaries after our marriage 25 years ago. His parents were still listed on his investments. Father-in-law passed 8 years ago, my mother-in-law has been cashing in and turning the funds over to me, realizing this is what my husband would have wanted. My husband had minimal insurance ($10K) so this is what's keeping me from having to sell my house etc. I've heard that if my elderly mother-in-law (91 and frail) has to go into a nursing home, the state (Medicare?) will come after me to return the money she had turned over to me, considering it as "gifts". Is there any way to protect myself from this? Draw up a document for her to sign stating where the money came from and why it's coming to me?