The jewels in Oliver Goldsmith's She Stoops to Conquer are far more than ornaments. They drive the secondary plot involving Constance Neville and George Hastings, expose the greed of Mrs Hardcastle, and give Tony Lumpkin the means to work his mischief. Their importance is therefore both dramatic and thematic.
The jewels and Constance's plight. The jewels are Constance's inheritance, but they are held in the keeping of her aunt, Mrs Hardcastle, who is reluctant to part with them. This is because Mrs Hardcastle wishes Constance to marry her son Tony, so that the fortune stays in the family. The jewels thus become the obstacle to Constance's union with the man she truly loves, Hastings.
Revelation of Mrs Hardcastle's greed. Mrs Hardcastle's grasping attitude to the jewels lays bare her avarice and her scheming nature. Her attempt to keep Constance's property under the pretext of family interest marks her as one of the play's comic targets.
Tony's mischievous intervention. Tony, who has no wish to marry Constance, secretly steals the jewels from his mother's bureau to help the lovers. The resulting confusion, in which Mrs Hardcastle believes the jewels are safe while Tony has actually given them away, produces some of the play's richest comedy and advances the intrigue.
Contribution to the resolution. The business of the jewels keeps the Constance-Hastings plot alive until the final unravelling, when Tony, declaring himself of age, renounces Constance and frees her to marry Hastings with her fortune intact.
In conclusion, the jewels are a vital plot device. They generate conflict, reveal character, fuel Tony's comic scheming, and finally help bring about the happy resolution, making them central to both the humour and the movement of the play.