Stefani is a female mouse with brown and white patches of fur. According to the model sheets, she is 5 1/2 ft tall.
She wears a collared shirt in different shades of lavender with cut out sleeves at the shoulders, a pair of black shorts that are above her thigh, a gold collar lapel pin. She also wears black and lavender sneakers.
In Season 3 her top was dark purple and lilac.
Stefani becomes Diane's new boss after Princess Carolyn suggests blogging work for her. She is the sister of Ralph Stilton.
Diane later meets with Stefani for a job interview. Stefani tests her loyalty by asking if she would be willing to write something negative towards her husband (ex-husband in Season 5) Mr. Peanutbutter if she had to. It is unknown what she said to this question, but she ended up getting the job.
In See Mr. Peanutbutter Run, Diane is now working at GirlCroosh.
In Hooray! Todd Episode!, While Todd is trying to distract her from looking at social media, Stefani addresses Diane about her articles, saying she finds it inspiring that she knows no one reads the stuff she writes about but she does it anyway.
In Commence Fracking, Diane is at a GirlCroosh meeting. One member is pitching an article about having a healthy sex life. Diane asks why they don't write an article about people who aren't having sex. Stefani pulls her aside and asks her if she isn't having sex with her husband.
Diane says that the campaign has been testing their marriage and that she can't wait for it to go back to normal. Stephanie encourages her to speak up but Diane says that she doesn't want to go against her husband. Stephanie says that she needs to "do you" and that right now no one is.
In Thoughts and Prayers, Diane writes a GirlCroosh article pushing gun ownership as a means of female empowerment. This article quickly gets the most hits on GirlCroosh.
In The Judge, Princess Carolyn, Ralph, and Stefani are on their way to Stilton Acres. Stefani tells her how much she’ll love it there, and Ralph tells her how much she’ll love The Feast of St Squeaky, the holiest of all mouse holidays.
He hopes his parents will like her, and Princess Carolyn assures him they will love her, and the two agree they’ll wait until after they warm up to her to tell them she’s pregnant. Stefani is not a problem as she is completely distracted by social media and her phone.
Princess Carolyn, Ralph, and Stefani have arrived at Stilton Acres. Ralph’s parents introduce themselves and the rest of the family. They offer her numerous things you shouldn’t eat/do when you're pregnant. Ralph is able to change the subject.
In The Dog Days Are Over, Diane arrives in Vietnam but gets a call from Stefani, telling her she wants more content for GirlCroosh. Diane tells her that she'll write a piece while she's in Vietnam. She calls it 10 Reasons to go to Vietnam: A GirlCroosh Personal Travel Guide.
Before Diane goes to Vietnam, It is also shown Stefani calls an exterminator when her cockroach IT staff try to unionize against her, referring to it as "negotiations."
In BoJack the Feminist, at GirlCroosh, Stefani tells Diane in disgust of the news of Vance Waggoner getting a Forgivie. Diane is also disgusted by this. Stefani wants Diane to go the award show to take Vance down and do some "Hollywoo hob-nobbing," and ask BoJack why Vance is going to star on his new show—a fact that shocks Diane.
In The Stopped Show, Diane meets with Stefani at Sandro's Place. Stefani explains that GirlCroosh is moving to video format and that she wants Diane to be the face of it. Diane says no to the offer, which shocks and confuses Stefani as she literally has never been said "no" to before, and she doesn't quite understand the concept of the word "no," because she was spoiled from the time she was young.
Diane then explains how she's an untrustworthy new source and a hypocrite after her actions. Stefani then explains to Diane what her problem is; that she often holds people and herself at a very high standard, allowing her to write juicy take-downs, but harrowing for her self worth. She explains that the world is already very unforgiving and standardized, and it's best to forgive each other. Diane asks if the content on GirlCroosh should be more forgiving, but Stefani blows off the idea.
She is the aggressive owner of GirlCroosh, often pressuring Diane to write more content, and she strives to expand GirlCroosh in Season 5. She often ignores others while trying to achieve her goals. When she starts texting, nothing can interrupt her, not even being poked in the eye. She was raised in an environment where she was never said 'no' to, so she often cannot process the expression of refusal.