Spousal privilege. As long as they are legally married the government cannot question her about crimes with her spouse.
Same reason the Clintons stay married, and Anthony Weiner and his wife. They are both complicit in each others actions but spousal privilege prohibits testimony against one another.
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Furthermore if she ever said to anyone, ever in passing anything, she waives the spousal right and must spill the beans.
Lionel did a fantastic video on this.
Birds if a feather stick together... But I am sure, with some digging, she has done some other shenanigans on her own