Is It Still Marriage Fraud If Only One Spouse Is Behaving Fraudulently?

My father (a US citizen) married a woman from Mexico in 2019. After they married her behavior did a complete 180 and she began treating him very poorly. Over the last 5 years my family and I have become increasingly suspicious of her motives. She quit working and has been traveling out of the country 10x per year without my dad and demands more and more of his money. He is now putting her through grad school and doing all of her work for her.

This week I found a huge collection of her journals while she was away in Mexico. They go back to when she met my dad in 2017 and contain entries all the way through mid-2024. Multiple times she writes about how much she and her family hate him and hope he will die so she can get his money and take it back to Mexico. She bemoans the prenup he had her sign and repeatedly accuses him of cheating on her despite the fact that he has never been unfaithful. She has also alienated him from his friends and family. He is not allowed to see us unless she is out of the country. She even accused him of having sex with my sister.

She also wrote instructions for adding a poisonous substance to food, but did not say that she had done it. However, about 2 years ago my dad experienced anaphylaxis after drinking a smoothie that she made for him (he had no allergies before this). For the last year my dad's health has gone hill abruptly with no clear reason. It started the day that he flew to meet me for a trip we planned together. He seems confused, his memory has gone, and he stumbles when he walks. He has had countless medical workups with no abnormal results.

Despite her behavior, my dad seems to be brainwashed into thinking that she loves him. She leaves sticky notes on the fridge showering him with affectionate words. The dates of these sticky notes coincide with journal entries about how much she hates him.

My understanding of marriage fraud is that it is a plan made by both parties to evade immigration rules. In this case, my dad is totally unaware of what she is doing. Does this still constitute marriage fraud?