She could sue you -- and by the laws of many US States, she'd have a damn good claim.

Sadly, this is true. What states do you and your mother live in? Currently, there are 30 filial responsibility states (Alaska, Arkansas, California, Connecticut, Delaware, Georgia, Idaho, Indiana, Iowa, Kentucky, Louisiana, Maryland, Massachusetts, Mississippi, Montana, Nevada, New Hampshire, New Jersey, North Carolina, North Dakota, Ohio, Oregon, Pennsylvania, Rhode Island, South Dakota, Tennessee, Utah, Vermont, Virginia, and West Virginia) that have passed statutes that cover “filial” responsibility laws. Meaning adult children may be required, and held liable, to pay for a parent’s medical bills. Definitely worth looking into if your mother resides in one of these states.