Both Erica Lindbeck and Vivian Nixon versions are what we're looking for.

Millie is very lively and cheerful. Often with a smile on her face and rarely standing still, she is a clear extrovert and isn't afraid to speak her mind. This is regardless to whether it's expressing her excitement or flipping off a coworker.

Also, as Millie is the bruiser of Blitzo's employees and seems to enjoy her job, it can be assumed she's tough and very violent as well.