I'm sorry to hear of your dilemma.
While it is perfectly legal for your ex to continue to use your last name as hers---I've got a couple doing that to me
--- lying to her employer is a bad idea---albeit not illegal either.
Because your ex is working for an agency, and not directly for her nephew, there would appear to be no clear conflict of interest of any kind in terms of her employer accepting money from state or federal agencies for services rendered by your ex in her capacity as an employee of Maxim. However, her employer may well have a problem with her providing nursing care for a relative---simply because of the way it works.
You will not have any result by contacting the state authorities---as I can assure you, no crime has been committed. However, her employer should be aware of her lying ways and you may report her for that, directly to the management of Maxim Home Healthcare.
I wish you the best in 2011.
Because I help people here, like you, for a living---this is not a hobby for me, and I sincerely XXXXX XXXXX abiding by the honor system as regards XXXXX XXXXX I wish you and your family the best in your respective futures.
Would you be so kind as to Accept my Answer so that I may be compensated for assisting you? Bonuses for greatly informative and helpful answers are very much appreciated. Thanks Again,