Starlight, Thorax, and their friends infiltrated the Hive and turned the changelings away from Chrysalis. But not every changeling was at the Hive. Twelve changelings were on the mission of infiltration. Twelve changelings remain loyal to Chrysalis.

Twelve changelings isn't a lot for getting revenge on Starlight Glimmer, and maybe conquering Equestria along the way. But Chrysalis has always been able to adapt.

Hopefully Starlight and her friends can too.