Who is the person Feste mentiones will be Olivia's fool? Do you agree with this? (act 3 scenes 1 to two)

According to Festes, whoever marries Olivia will be her fool.

"No, indeed, sir; the Lady Olivia has no folly. She will keep no fool, sir, till she be married, and fools are as like husbands as pilchards are to herrings; the husband’s the bigger: I am indeed not her fool, but her corrupter of words."