To dream of a nymphomaniac represents your perception of yourself or others being obsessed with having a good time. Having to have a good time no matter what.
Negatively, a nymphomaniac may be a sign that you or someone else is dangerous about having to have enjoyable experiences all the time. Going too far or being risky to keep enjoying yourself. It may also be a sign that you or someone you know is not thinking of others feelings while enjoying everything they want.