Madam, there is at the gate a young gentleman much desires to speak with you (1.5.99).
I am not sure madam.
Malvolio, go fetch him off; say I am sick or not at home. Whatever it is, you shall dismiss him.
From the Count Orsino, is it (1.5.101)?
Cesario's attempt to woo Olivia
Most sweet lady, my lord loves you!
I cannot love him! I am well sure that he got his answer long ago.
Olivia's Answer to the Duke's Love
Farewell, madam Olivia.
Go back to your beloved Duke and tell him that I cannot and will not love him! Do not let him send any more messengers...unless perchance it is you who comes again.
After a while, Maria comes to say that there is a young man at the gate waiting to see Olivia, which is Cesario/Viola. Hence, Olivia sends Malvolio to receive the young man. But, Cesario refuses to leave until he sees Olivia which leads to Olivia being captivated and she decides to let Cesario speak with her.
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Viola, who is disguised as Cesario, starts to return the love speech of the Duke to Olivia, however, Olivia refuses to hear all of it. Through Cesario’s skills of praising Olivia’s beauty, he is able to get Olivia’s attention. Olivia, intrigued, begins to turn the discussion about Cesario.
Olivia falls for Cesario
Run after that petulant messenger, the Duke's servant. He insisted on leaving this beautiful ring with me without asking whether I desire it or not. Hie, Malvolio, fetch him.
After their discussion, Olivia sends Cesario back to the Duke and tells him to tell the Duke that Olivia does not love him and most probably never will. Though, Olivia suggests that Cesario come back and speak to her about how the Duke takes her answer.
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Hi Keira!
When Cesario leaves, Olivia commands Malvolio, her steward, to go after Cesario with a ring in which she pretends is his. But it is not his and is simply a way to show her love to Cesario. To her surprise, Olivia realizes that she is very much in love with Cesario.