My mother is on medicaid in a long term care facility. She is to receive a sizeable amount of money from her deceased niece who died without a will.

You might be able to disclaim the inheritence and have it pass to you and your siblings, if any.  You should contact the attorney working for the estate and see if a disclaimer is possible.  There are certain rules to be able to disclaim, like timing and whoo the asset passes to after disclaiming.