There could be some mental issues involved. I also know of a marriage where the man kept accusing his wife of adultery until they divorced after being married for decades. He said his first wife had cheated on him, and he had affairs while living with his second wife. Maybe he was 'projecting' that on his wife. The 'spirit of jealousy' is also mentioned in the Old Testament.
If I were you, I'd point out to her that a woman divorcing her husband has no basis in scripture and wouldn't be considered valid under the law revealed in scripture. I might try to get a pastor involved to do counseling and to try to reason with her. You want someone solid in the word and kind of 'fair' not the kind who always assumes the man is guilty of adultery. Also, someone who believes in wives submitting to their husbands. There is a new 'narrative' out there when it comes to marriage that some authors, 'Christian counselors' and pastors promote that involves the wife doing something drastic, like threatening divorce or divorcing, to bring about some change in her husband. Sometimes it's for much smaller things than adultery. The idea is to get the husband to submit to the wives agenda.
If she really wants to divorce and she's moved out and filed papers, that's a serious situation. Don't compromise your integrity and sin to get her back. (You can read Job about temptation to compromise your integrity. His friends were trying to get him to admit to things he didn't do. His wife was trying to get him to curse God and die.) If your wife threatens divorce as some kind of power play (in this case to get you to admit to something you did not do) you have to be careful about giving in. In your case, I don't see how you have any choice, ethically, except NOT to give in. It's one thing to lie, which is bad. It's even worse if you are lying about the Holy Spirit. You don't want to contribute to that if you are completely innocent of her charges. If she says she will divorce and you forbid it and say you don't believe she will because she fears God, that may put an end to it. If it's only something she throws up in conversation, you might turn out better if you just say she won't divorce rather than acting all scared, begging, or starting to jump through hoops not to get her to threaten divorce. If she sees that you jump through hoops for her not to divorce you, she may come up with more hoops if she has some serious control issues. If she mentions divorce, that's an issue you have to revisit later. She needs to apologize for throwing that out at some point. The relationship is not back to normal unless that is resolved, IMO. Threatening divorce is not cool. It's not okay. You say you haven't cheated on her. She shouldn't be doing that. She's wronging you, and your position, if that is the case, should be that she has done you wrong and that is not okay. And the issue still needs to be resolved. At some point, she should apologize and acknowledge she shouldn't threaten divorce.
Her demanding you take a polygraph and not taking one herself creates a really bad dynamic. If she's not guilty of anything, that may be a really controlling thing to do. It may point to a really bad power dynamic in the marriage, where she blows up or gets upset about something and you do stuff to placate her, and she always gets her way. That's not good as far as the headship and submission aspects of the marriage go.
If I were in your shoes, I might tell her that since she thinks the Holy Spirit is telling her things about you that you plainly know to be false, that she has 0 credibility in your eyes when it comes to saying what the Holy Spirit said, and encourage her to submit to you as her husband, since the Lord can lead her in that way. If a pastor and other Christians you bring in to help can also point out her error, maybe there is a chance she will open up some. II Corinthians 10 spiritual warfare has to do with casting down imaginations. It has to do with ideas, possibly even arguments and thoughts. It might even help if you had someone minister to the both of you who had some experience with deliverance if she needs some help in that area.
That being said, do consider whether you may have sinned in your heart and that she's picking up on it. Jesus said that he that looks at a woman to lust after her has committed adultery with her in his heart. If she mentioned women you'd looked at with lust, you should consider that. If she said the Lord told her you had sex with them when you hadn't, that's another matter. Or if she chose women you had no attraction to at all and you know you haven't sinned in regard to them, that's also another matter.
Btw, if you know anyone who is genuinely gifted in prophecy and related gifts that she respects, you might bring that person into the situation to counsel and pray with you. If she believes the person hears God, and he gets a word of rebuke for her, that might cut through some of the junk in her mind.