Stefani is a female mouse with brown and white patches of fur. 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.
According to the model sheets, she is 5 1/2 ft. tall.
Stefani becomes Diane's new boss after the Hank Hippopopalous' incident and mutual interests. She is the sister of Ralph Stilton.
In That Went Well Princess Carolyn suggests that Diane work with Ralph's sister because she's creating a new company, GirlCroosh.
In See Mr. Peanutbutter Run Diane is now working at GirlCroosh. Stephani tests her loyalty by asking if she would be willing to write something hurtful towards Mr. Peanutbutter if she had to.
In Hooray! Todd Episode! 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 while Todd is trying to distract her from looking at social media.
In Commence Fracking Diane is at Girl Croosh sitting in a meeting where one of the people 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.
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.
Princess Carolyn is offended by the racist tradition's The Stiltons practice but as they are leaving Ralph tells his parents they are serious about their relationship together.