|“||You said he'd win the game. You're a fake psychic, fake-psychic boy!||”|
|— Sienna to Booker|
Sienna was portrayed by Jenna Davis.
Sienna is popular and influential, especially through the social media app, Peanut Face where she has a lot of followers who follow her and whatever she likes. She is sweet and loves dogs as seen in how much she cares about her dog, Mr. Manchego. Sienna is aggressive and seems to result to violence when someone messes with her as seen in the way she leads other students to attack Booker for being a fake psychic and how she aggressively demands her money back from Nia and Tess.
Sienna becomes Levi's pal on Peanut Face which influences a lot of her friends to follow Levi too. When Booker gets a vision of Sienna's puppy stuck in the rooftop, he takes advantage of the situation to rescue the puppy and get Sienna's follow. He asks Sienna something bad is going to happen to the dog but Sienna doesn't believe him until her mom calls in saying the dog is lost. Sienna is devastated but luckily Booker saves the day by rescuing Sienna's dog, Mr. Manchego.
Sienna starts suspecting that Booker stole the dog because first, he said something bad would happen to the dog and then he rescued him. She starts calling Booker a dognapper, which pushes Booker to tell her that he's psychic. At first, Sienna doesn't believe him but after seeing that Mr. Manchego likes Booker, she believes him. She promises not to tell anyone. But then, she posts about it on Peanut Face, causing all the kids at school to start calling Booker psychic. Later, Sienna joins the rest of the crowd in getting fake visions from Booker. After finding out that Booker is telling them fake visions, Sienna leads the rest of the kids to run after Booker and Nia.
Sienna is fascinated by Nia's jacket and says that she would do anything to wear it. This gives Nia an idea to start renting the jacket for money. She pays to rent Nia's cape the next day before detention, but she returns it and demands her money back after noticing the new trend from Zeena. When she buys one of Nia's malfunctioning cell phone pouches, she demands a refund and even threatens to beat them up if they don't give her money back.
As the girls make Jack-O-Lanterns on the roof, Sienna and Zeena begin to suspect that Nia has made up her Halloween date Miles, and take Tess' wincing whenever his name is mentioned as confirmation. The pair then begin using air quotes when saying his name to Nia's annoyance. Later the pair, dressed as witches for the school party, meet Miles and are instantly charmed by him. They apologize to Nia, and even sigh when they see the couple hug.
After introducing new neighbors Jamie and her sister Amber to Booker and Levi, Sienna reveals that she and her family are leaving for a weekend outing. She later allows Booker and Levi to dogsit her dog, Mr. Manchego, after the pair volunteer their services. As Sienna leaves Booker with Mr. Manchego's special treats, she says goodbye to her dog and tells him not to pee on anyone, words which the canine, much to Booker's misfortune, does not heed.
Sienna attends Nia’s party, and she was the only one who didn’t want to dance with Booker. Since The Guntz and Curtis wanted to dance with Nia, and Zeena wanted to dance with Booker.
Sienna participates in the raffle hosted by Booker and Nia and wins the prize of meeting Lil' Z for smoothies on the roof of their apartment building, 352 Hauser Avenue. While Sienna is walking up to the roof, Nia says that she can only talk in small bursts, not full sentences to Lil' Z, which Sienna gets a little suspicious about. When Sienna and Nia arrive at the roof, Lil' Z greets and begins to talk to Sienna, whilst Sienna only responds with "excited.", and is quickly made to sip a tiny smoothie, before being rushed away, after taking a quick selfie with her prize. After the meeting, Sienna makes a post with an image of her and Lil' Z and a caption of "best raffle prize ever". Later in the week, Sienna and her classmates attend the Ravenous Fashion Show.
While improving her posture, by balancing a book on her head, Sienna encounters Nia in the cafeteria. Nia jokes that it's not what the phrase "knowing the answers off the top of your head," means. Sienna explains she is preparing for her Cotillion class. Before she continues to practice, Sienna does note that Nia's current outfit is "farm fabulous." Later Sienna attends the Carver Cotillion class' "High Hopes High Tea," and is complemented by the teacher, Principal Kwan, for her posture, but gets a mini-lecture on the use of rhetoric in conversation. Upon hearing that Kwan sometimes utilizes a fork as a back scratcher, Sienna muses to herself that she hopes the larger tined utensil she is examining is not the fork in question. Kwan then calls upon Sienna to deliver a toast. Standing up and introducing herself, Sienna declares that due to the class, she now knows that she is as beautiful inside as she is outside, and thanks the class. Kwan stated that was not a toast and Sienna raises her glass and quickly adds, "Cheers." Tess is then called to offer her toast. Sienna voices her surprise to see the other girl wearing sneakers with her dress. Tess implies that Sienna is mad because her high heels are not as comfortable, and Sienna seems to grudgingly agree. After Tess finishes her toast (while using a basketball), Sienna is somewhat disgusted that no one told her to bring props.
- Because (first appearance)
- All Sewn Up
- New Dog, Old Trick
- It's Your Party and I'll Spy If I Want To
- Keepin' It Real
- Dress to Express
- What About Your Friends? (mentioned)
- As revealed in Because, she likes avocado toast.
- She has a dog named Mr. Manchego.
- She and her family live in apartment 2C of 352 Hauser Avenue. In The Foreign Identity, it is hinted that her last name might be Davis, or at least, is the surname of a neighboring family on the same floor.
- In Because, a final scene was cut where she and Booker reconciled.
- She is very chatty.
|“||Mr. Manchego just doesn't give kissie-wissies to just anybody.||”|
|— Sienna to Booker|
|“||It was fast, and weird, and I’ll never forget it!||”|
|— Sienna about her picture with Li’l Z|
| The image gallery for Sienna may be viewed here.