2 scenarios are plausible:
1) It is just a way to broaden the base, especially if she is appealing to female viewers as well. She's attractive, so that will definitely hit the male demo, and if she's smart, sassy and competent, that should appeal to the female demo, and the guys-who-like-attractive-smart-and-sassy-women-in-their-fiction demo.
2) They couldn't find anyone to play Jimmy as a man.
Either one, or both are equally likely, IMHO.
1) It is just a way to broaden the base, especially if she is appealing to female viewers as well. She's attractive, so that will definitely hit the male demo, and if she's smart, sassy and competent, that should appeal to the female demo, and the guys-who-like-attractive-smart-and-sassy-women-in-their-fiction demo.
2) They couldn't find anyone to play Jimmy as a man.
Either one, or both are equally likely, IMHO.