Shanilla is one of the few people lucky enough to be able to see Billy due to her possession of one of his bracelets.
People at Beverly Heights don't really seem to pay attention to Shanilla. Likewise, Shanilla doesn't really seem to pay attention to them.
She appears to be a good friend to Spencer and Billy. When she hangs out with them and Rajeev, she is generally respected (not as much by Rajeev as Spencer and Billy, but he is her brother, after all). Shanilla seems to be more loyal to her friends than Rajeev.
Shanilla is especially amiable towards Spencer, due to her crush on him. In Billy Joe the Scholar, she was more than willing to abandon logic and reason to defend Spencer (along with his mistreatment of Billy), and when she saw him in his freshly ecto'd state in The Ghost of Spencer Wright, she was visibly upset by the prospect that he might have died in order to become a ghost. (In contrast, Rajeev was more confused than anything.)
However, she does not overtly fawn over him as much as Rajeev fawns over Lolo, partly due to the fact she hasn't told anyone about her crush on Spencer.
Shanilla is a very grounded girl, even more grounded than Spencer is. Because of these no-nonsense tendencies, she is less prone to getting caught in mischief the way the boys are. However, if Spencer asks her to help out with something, she will be there regardless of how ridiculous or dangerous the situation is.
One example of her being more grounded than her peers would be that she did not get jealous of Lolo and Spencer's "relationship" in Lolo In Love, because she understood that Spencer wanted no part in it, while Rajeev flipped out and did not give Spencer enough time to explain himself.
It can be inferred that she is a good student due to Principal Ponzi's general tolerance of her. She is also evidently a good friend, seeing as Billy and Spencer treat her with great respect.
- As seen in Billy's Achilles, she is very good at assembling furniture according to instructions.
- One of her fantasies, as shown in A Place In The Sun involves people text messaging her saying that she is "the prettiest girl at the school."
- As shown in The Candidate, she seems to know something about computers, as she was focused and confident when attempting to hack into Lolo's computer.