I have a six year old also, and he is very insecure, he is extremely a head of his classmates when it comes to his academic skills, but when it comes to his social behavioral skills he seems to be more on a toddler level. I am trying to teach him independence by learning to work on school work and completing before he asks for my help, and also trying to teach him to occupy himself. I feel he has been babied too much and now we are paying the fine. HOpe that helps.
The first 'culprits' to examine when a child's functioning changes rather suddenly are illness and changes in the youngster's environment. I'm assuming she's physically well and that she has not been ill. Relative to changes, the strat of kindergarten can be a daunting developmental challenge, even when children have been in pre-school. The presumptive cause of her change would be the transition to kindergarten. But it may be worth an assessment by a child psychologist. It's good that you are aware of your predisposition against a couple of the traits she is displaying. Be careful you are not acting in a critical way with her or conveying a sense of disapproval. Be supportive and encouraging, without heaping a lot of stress on her.