The Misadventures of Zoey & the Witch by Judy Gloom

Zoey and the Witch is a series of novelettes (around 7,000 words each) about 15 year old Zoey navigating high school and family life with the help of the exotic, 24 year old witch, Anastasia - and of course - a little magic.

Book #1: Salem Black Hat Society
As usual, Zoey went to the creepy old, abandoned mansion at the end of the street to be alone. But for the first time ever - there was a light on in the kitchen!
Zoey stood by the window, listening, until Catkin, the cat, hissed at her and Anastasia trapped her with some kind of spell. Turns out Anastasia has inherited the mansion and is in town to fix it up and sell it. She's also prepping for the final test of her Witch Correspondence Course - an invisibility spell - that gets her into the Southern California Chapter of the Salem Black Hat Society - the most prestigious International society for witches. Zoey helps Anastasia finally get the spell right, and in the process, realizes she could use some of these spells for an unbelievable adventure of her own.

The series features witches, flying brooms, spells, grimoires, haunted mansions, ghosts, bullies, mean girls, discussions of body issues, depression, cutting, using drugs, divorce, step-parents, half-siblings, and first love and crushes, written lovingly for all the spooky kids out there.