What does Olivia reveal about herself from her words and actions in Act IV of Twelfth night?
In Act IV of Twelfth Night Olivia reveals through her words that her gender role does not preclude her from asking Cesario/Sebastian to be ruled by her. Later in Scene iii, she reveals that her gender role does not restrict her from making wedding arrangements and asking Cesario/Sebastian to wed her.
In Scene 1, Olivia comes upon one whom she thinks is Cesario while he is engaged in a quarrel with Sir Toby. It is not Cesario, though. It is actually Viola's/Cesario's twin brother Sebastian. Olivia takes Sebastian for Cesario and, after breaking up the quarrel, asks Cesario/Sebastian to "be ruled" by her. This is more of a forward action than the gender stereotype would expect from an encounter between Olivia and Cesario/Sebastian.
In Scene 3, Olivia reenters the stage in the company of a priest. She has independently made wedding arrangements, brought the priest and proceeds to ask Cesario/Sebastian to accompany her and the priest to the "chantry" (chapel) to be married. This similarly is more of a directing, orchestrating role than the gender stereotype would suggest as a resolution between Cesario and Olivia.