I need to know which nymph and which shepherd's idyllic vision you are talking about in order to tell you the flaws she finds. For example:
* Are you thinking of a specific myth or poem?
* Is this a fictional story you're reading?
* What are the details of the shepherd's vision and the nymph's perspective?
Once you provide me with more information, I can help you analyze the situation and identify the flaws the nymph finds in the shepherd's idealized view.