Queen Twilight's forces consist of Featherweight who is cowardly and skilled at communicating with the changelings, Lightning Dust who is brash and unswervingly loyal, Rumble who relies purely on his physical strength, and Dinky Doo who is her own protege. In other words, poor stand-ins for Fluttershy, Rainbow Dash, Applejack, and herself before her Heel–Face Turn. It's very possible she picked these ponies trying to replace her friends.