One interesting feature of this poem is that there are absolutely no adjectives in the poem which describe Celia. This is somewhat unusual for a love poem of the period, in which extensive descriptions, and often extended similes, are commonly used to describe the beloved. Rather than actually describe Celia using adjectives, instead Ben Johnson uses strong action verbs such as "drink,' "pledge," "wither," "sup," and "breathe." This is a feature of the classical pared-down style with which the "school of Ben" opposed some of the flowery excesses of ornament common in the Petrachan tradition.
If you have been asked to come up with adjectives for an assignment, you will need to infer a description of her from the narrator's attitude. But, interestingly, the woman herself is a complete cipher -- the narrator talks about his own emotions a great deal, but doesn't seem to have any clear picture of her in mind nor does he include any details that would enable us to distinguish her from any other woman. Perhaps that is why she rejected him!