Final answer:
Beatrice is using a playful metaphor to discuss the giving and taking of affection in a romantic relationship, suggesting that her love interest once won her heart deceitfully and now she has 'lost' it.
Step-by-step explanation:
The lines spoken by Beatrice refer to the metaphorical 'heart' that was lent and then lost in a game symbolic of love and courtship. Beatrice comedically suggests that she had given her beloved interest on his 'single heart' by offering her 'double heart', indicating a playful exchange of affection. However, she then notes that she has 'lost' it because the beloved previously won her heart through deceit (false dice). The underlying context indicates a romantic jest, playing upon the metaphors of games of chance to describe the complexities of love dynamics.