Chitter was a clone of Taylor Hebert created by Echidna. She shared her memories, but, like all Echidna clones, felt a driving desire to destroy everything her original cared about. She was only named in the chapter tags.
Chitter or Scurry as she was originally labeled in the tags, had the ability to control rats, a variant on Taylor's ability to control bugs. She covered herself in rats, as well as siccing them on her enemies. Her name is a pun combining the chittering sound of rats with Skitter, with Scurry being a reference to the scurrying of rats.
Several other clones of Taylor Hebert were created that shared her ability to control bugs, but were otherwise similar to Chitter. In fact like the Famine Engine the clones use of their abilities interfered with Taylor's ability to direct her bugs.