Welsh international forward Lander joins from Arsenal, having previously spent many years with Watford.
Plewa is another forward capped by Wales and comes in from Bristol Academy, who she played with for the last four years.
Defender Boyer is recruited from Millwall Lionesses, having earlier picked up an FA Cup runners-up medal when with Charlton Athletic.
Chelsea will be playing their FA Super League home games at Ryman League Premier Division side, Tooting & Mitcham United FC's Imperial Fields Stadium (pictured).
