Beau Fitzgerald (born 1995 in Port Lincoln SA) uses this phrase all the damn time, and we still have no clue what the heck it means.

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.