Because there's never enough girl bugs.
Welcome Vasilisa! Vasya for short.
She is a velvet ant, one you can more commonly find on Eurasia.
She is a psychologist of sorts, or as close to a psychologist as you can get in a bug society.
She comes from the North, losing her arm somewhere on her way to the Wasp Kingdom. She comes after the whole Wasp King deal and finds the situation both curious and horrifying. She is used to the bugs suffering from the stress of survival, not the aftermath of a mindcontrolling tyrant. She admits she might have a bit of an unhealthy interest in mind control, but nothing that prevents her from helping the others.
(Kali and Kabbu situation would be very interesting to her, too. Leif's situation should be considered a case study for many fields of science, including psychology.)
All in all, she is a well-meaning if at times off-putting bug.