Diana is the young, virginal daughter of the widow. In the play, Bertram tries to seduce her, but she ends up tricking him into sleeping with Helen.
If you've read Romeo and Juliet, then you're probably thinking that Diana's last name (Capilet) sounds awfully familiar. Still, Diana is no Juliet Capulet. Let's face it: Juliet doesn't exactly shy away when Romeo shows up at her bedroom window. If anything, Diana is more like the virgin-for-lifer Isabella from Measure for Measure; Diana insists throughout All's Well that she remain chaste until she's married, despite the fact that dreamy Bertram puts the moves on her. At one point, she even declares that she is never even going to get married:
Since Frenchmen are so braid,
Marry that will, I live and die a maid. (4.2.84-85)
In other words, Diana is so turned off by Bertram's sleazy behavior that she swears off men, permanently. Hmm. This is probably why Shakespeare named her after Diana, the goddess of chastity, don't you think?
In the play, Diana's character gives voice to the sixteenth- and seventeenth-century idea that a young woman's virginity is a kind of "treasure" or "jewel" to be guarded and protected at all costs.
Check out this passage where Diana compares her chastity to Bertram's family ring:
Mine honour's such a ring.
My chastity's the jewel of our house,
Bequeathèd down from many ancestors,
Which were the greatest obloquy i' th' world
In me to lose. Thus your own proper wisdom
Brings in the champion Honor on my part
Against your vain assault. (4.2.55-61)
Here, Diana calls her chastity the "jewel" of her house. She reminds Bertram that, if she were to lose her virginity to some guy that has no intention of marrying her, she'd bring disgrace ("obloquy") to herself and her entire family. What's more, her hopes of ever getting married would be ruined. This idea was pretty common in Shakespeare's day. In Hamlet, Laertes warns Ophelia against premarital sex and tells her to guard her "chaste treasure" (1.3.35). One popular Elizabethan handbook even says that a woman's virginity is "the best portion, the greatest inheritance, and the most precious jewel" of her dowry (source: A Godly Form of Household Government, 1603).
We know what you're thinking. Why was chastity such a deal maker or breaker in Shakespeare's day? Well, in the sixteenth and seventeenth centuries, eldest sons inherited all their fathers' wealth, titles, and land. (In the case of Bertram, an only child, he inherited the title of count, his dad's money, and the family ring.) A man's marriage to a virgin ensured that a man's children were legitimate and that the family wealth could be passed on from generation to generation. Basically, marrying a virgin was a big deal, especially to noblemen who wanted to make sure that their kids were really theirs.
The proof is in the pudding: check out what the king of France says to Diana at the end of the play:
If thou be'st yet a fresh uncroppéd flower,
Choose thou thy husband, and I'll pay thy dower. (5.3.372-373)
Translation: The king is going to let her pick any husband she wants and he'll even pay her dowry, but only if she's still a virgin ("uncroppéd flower). Hmm. Maybe the king should go back and read Act 4, Scene 2. We're pretty sure Diana said she doesn't ever want to get hitched. Go to "Themes: Sex" for more on this.