Someone whose sexuality and/or fetishes fluctuate rapidly, changing seemingly at random, and aren't fixed unless directly observed.

A bastardized version of the Uncertainty Principle and Observer Effect of Quantum Mechanics, Applied to ones Sexuality.

A pick me is a woman that is willing to do anything for male approval. She will embarrass or throw other women under the bus to achieve this goal. The unfortunate thing about a pick me is usually the men they are trying to seek approval from are of poor quality and treat women badly, leaving little real benefit for the pick me.