How likely is immigration to view a marriage between an 82 yr. old US citizen and a 56yr. old illegal immigrant as appropriate?

My 82yr. old father married a 56 yr. old illegal Philipino to get her a green card and to reinstate her driver's license. Initially she was adamant about having a prenup so we didn't think she was after his money and he insisted she was not going into the Will. She offered to divorce him after 2 yrs. if we still didn't approve of the marriage. Of course they told their immigration lawyer they were in love. This woman is bleeding him dry and he's a willing participant. We can't have him declared incompetent because he isn't, he's simply blinded by her attention. We called ICE, DE state and local authorities, their immigration lawyer and the lawyer who is rewriting his Will and legal papers to include her, with no success. Everyone has told us it's not illegal for 2 consenting adults to marry. It appears that she has more rights than we. Within 2 months of marriage she has quit her job, failed out of nursing school and convinced my father to make her his Power of Attorney and to include her in his Will. They were married in DE without her birth certificate. Is it possible that the marriage is not legal? I hope immigration will include family members in the decision making process. This woman has told me to my face that if my father had not married her or would not financially support her through this process she would not be in a relationship with him. She would have found another way to stay in the U.S.