What's the Name of That Book??? discussion

i can't remember the name or title but there's this girl who goes to this school i wanna say she tries skateboarding with her older brother at one point and I slightly remember that her dad has a girlfriend who she gets in fights with due to her not wanting the lady to replace her mom because she pushed her real mom down the stairs, due to her not paying attention to her due to the mom having cancer and dying soon after. (goric i know) i remember she gets sent to some weird boarding school where their always eating, like candy given in the desk, cotton candy on the playground, but the wood chips on the playground are made of bone (future thing sorry 4 spoiler) she gets picked on a lot but is able to make one semi friend, then she gets served her favorite food in the cafeteria marzipan and every other student is eating heaping piles of food and under some sort of spell, and close to the end she finds out that the principal is a witch and plans on killing all of them, but wants her to be a part of her coven or something, and she pretends to agree but then pushes her and the other witch who was the nice teacher into the pot killing them both. I remember reading it in about 5th or 6th grade (I'm a 10th grader so not to long ago, just not the greatest memory and I had moved schools so I cannot get in touch with that teacher anymore) and I think there was a part in the story where they were three witch sisters but they killed one or something I cant remember. and google has been no help so I went to the next best place.

The Sinister Sweetness of Splendid Academy

The Sinister Sweetness of Splendid Academy by Nikki Loftin, Lee's suggestion