The Seance - Dark Summons, #1

Ninth grade can be a nightmare when you don't fit in at school, your crush chooses someone else, and your parents tell you they're having a new baby. Abby was prepared for normal high school problems. She wasn't prepared for a demon. Abby has always been fascinated by the paranormal, but after an ill-fated séance, she discovers not all Spirits are benign. A dark entity unleashed during the summoning sets out to destroy Abby, and within days, she loses her best friend, incurs the wrath of her parents, and becomes a prisoner in her own home.
With time quickly running out, she assembles an unlikely group of helpers: the most hated guy in school, a retired psychic, and the cute clerk from her favorite bookstore. Unless the demon is defeated, Abby and her new baby brother won't stand a chance.