Rachel's bio is available in the minor character docket and is as follows:

This is my personal favourite of the series. It's Rachel and Cindy, a duo of scrappy villains plotting to destroy Chester's confidence for a $50 gift voucher. Rachel has the most guttural and crass language used on the show. She's intended to speak with a heavy smoker's cough, parallel to Lola from Big Mouth (2017), and may be more desirable to masculine voice actors. Cindy as her sidekick contrasts with a whining shrill voice and supposedly begs for food on the beach in her spare time.

Voice Acting Tip: Rachel's androgynous, masculine and/or disgusting tone can be difficult to master. Her "heavy cough" when being pushed over the garden wall is designed to be her most memorable joke (much like a catchphrase) and it's what I'll be looking at to cast the role. Pretend you're throwing up a hairball and you'll be right as rain.