The nymph catalogues the many things that the shepherd promises her in these two lines. By listing them, the nymph separates each item from the metaphor the shepherd ascribes to it. In this way, she undercuts the metaphorical beauty with which he imbues these items. They form a stark list with little importance.
The “flowers” that the nymph refers to here are the flowers that the shepherd promises to turn into clothes for her in Marlowe’s poem. Specifically, she means roses, posies, and myrtles. While the shepherd focuses on the beauty of the flowers and of the objects he gives her, the nymph focuses on the ephemeral nature of the flowers and their inevitable fading.
