It is heart wrenching to watch someone you love do things that are not in their best interest. Sometimes all you can do is step back and let them do it. Try not to focus on what she is doing with her inheritance, there is not much of anything you can do about it but give yourself an ulcer. Your father probably knew when he set up his estate that this was a good possiblility, (considering her history of money issues) and he still chose to give her the funds in a lump sum amount. Maybe in his own way he is saying that it is her choice now on how she handles her inheritance.