Under what condition does the Nymph say she would be the Shepherds love?

The Nymph states she would be the Shepherd's love if he could promise her a life of true devotion and fidelity. Specifically, she desires assurances that he would remain faithful, provide her with gifts, and commit to a lasting relationship. However, she ultimately expresses skepticism about his promises, recognizing that such assurances often lack sincerity.