Vashti, I found nothing in my research to explain or support your behavior. You may have had a legitimate reason for rejecting King Ahasuerus’ request. I may never know. I can only guess based on what the scriptures tell us.
1. You both were probably drunk and feeling quite emboldened. We know he was.
2. You may have decided to become a feminist at that moment. Were you tired of parading around in front of a bunch of drunken men so the king could puff out his chest?

3. Were you just tired? You had been partying for seven days also.

Whatever your reason, it wasn’t a wise move. Girl, you knew your man. You knew he was a proud man who would be drunk and showing off. You also knew those princes. After all, the wives were at your banquet. I’m sure they had some input. Did they put you up to it? 🤔

That said, I did see how you were WRONGED!

I don’t believe you thought or knew you were in danger and here is why. When you denied  the King’s request, he asked his advisors what did the law say regarding your behavior.  They never answered that question and the King was too drunk and angry to notice. Instead, for their own fearful and selfish reasons, they convinced the King to be harsh in punishing you. Why? So their wives would not oppose them. Got to keep them in their place.
King Ahasuerus did not respond to you according to the law. He created a new one that he later regretted.

Vashti, you were Wrong and you were Wronged!