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I'm sorry to hear about your situation. First of all, you need to understand that Washington is an at-will employment state. At-will employment means that without a contract, you have no contractual or other right to employment with the company. The company is entitled to fire you for any reason: a good reason, a poor reason, or no reason at all--as long as the company does not fire you for an illegal reason (race, gender, age, religion, etc...). But it extends beyond firing, to hiring, promotions, demotions, wage cuts and raises, disciplinary actions, and even scheduling. Unless you can show that this was done in violation of a contract, union agreement, or a clear violation of an unambiguous and binding clause against the employer, or that it was done because of some minority status (age, race, gender, religion, disability) that you have, then they do have this discretion .
I understand that you're insulted and embarrassed. Now the fact that you're in the top 1% of talent does not have any legal basis whatsoever. I do think that it means that they should treat you better, as you obviously have the skills and knowledge to go to a different employer. But legally that has no bearing on the situation.
The fact of the matter is that there have been no laws that have been broken here. I absolutely agree that it's unethical, immoral, and illogical to treat you this way. But it's not illegal. If I were you I would complain to this person's superior(s). But there's nothing that you could do through the courts or the EEOC from a legal recourse perspective, I'm sorry to say. The at-will doctrine will control in this manner, as they would still have discretion as to how they conduct the investigation. The closest thing that you could have a case on would be based on fraud, as she tried to get you to sign something that was untrue. But the fact is that you didn't, and as such you wouldn't have incurred any quantifiable damages as a direct result of that fraud (which would be needed to be proven by you to have a case of fraud).
I know this is probably not what you wanted to hear, but it is the law. I hope that clears things up anyway. If you have any other questions, please let me know. If not, and you have not yet, please rate my answer AND press the "submit" button, if applicable. Please note that I don't get any credit for the time and effort that I spent on this answer unless and until you rate it positively (3 or more stars). Look for the stars on your screen (★★★★★). Thank you, ***** ***** luck to you!