Ann Powers has a good obit in the LA Times:
Their quality has to do with Greenwich's gift for capturing the frisson of a decision almost made, a change that hasn't quite come, and which could still go either way. The voices for which she wrote, young and nearly always female, had a natural waver. They belonged to the kids who would change everything: multicultural girls such as Barbara Alston and Dolores "La La" Brooks of the Crystals, Ronnie Spector of the Ronettes and Mary Weiss of the Shangri-Las, girls who aspired to certain feminine ideals but also wished for a certain freedom promised by the changing attitudes of their time.
Here’s one of Greenwich’s greatest songs: