How is the theme of love portrayed through Beatrice in Much Ado About Nothing?
I would want to argue that you can't just look at Beatrice alone to explore the theme of love through her character. Let us remember that Shakespeare presents us with two couples, and interestingly each couple seems to suggest something very different about the nature of love. Therefore we must include Benedick in this discussion.
Of course, both start off swearing that they will never marry, and the "merry war" that rages between them overtly suggests their mutual dislike. Thus it is that Benedick states that he "loves none" and Beatrice says that she is of his "humour" in her aversion to marriage. However, thanks to the good deception practiced by Don Pedro, both Beatrice and Benedick are made to believe the other is in love with them, which in turn makes them realise that they love the other.
A key scene for me in the kind of love that their relationship represents is actually towards the end of the play, in Act V scene 2. Although at this stage they are clearly in love, the "merry war" of puns and verbal duelling continues between them. At one stage, Benedick interestingly says:
Thou and I are too wise to woo peaceably.
This in a sense shows the nature of their love. Compared to the silence and submission practised by Hero in her relationship with Claudio, Beatrice is never going to be a door mat, and yet, Benedick says, this is because of her wisdom rather than anything else. A maturer, more realistic type of love is thus presented to us through the relationship of Beatrice and Benedick. They will continue to mock each other and to playfully fight, but their relationship will be the stronger for it.