The גמרא, מגילה יא עמוד ב
Three lines from the bottom
בא שטן וריקד ביניהן הורג את ושתי
Satan came and danced amongst (between) them and killed Vashti
Is that clear enough?
What are you trying to clarify, that Vashti was killed? Midrashim were already quoted.
How Vashti was killed? The gemara doesn’t say that.