Secret Witch by Letty Frame

Death always has a way of bringing secrets to light. But when the only person who knows the truth is gone, how do you figure out what was real? It’s a shame the dead can’t talk.
Elzora Miller is a human. Wait, that’s not true. It turns out she’s actually a witch. When her grandma dies, a binding spell placed on her as a babe breaks, and the truth comes to light. With no time to adjust, Zoe’s moved to Mitagus, the realm where witches live and enrolled into the Whisperfelt Institution of Magicae.
Zoe’s convinced her new life is a hallucination—a side effect of her anxiety disorder—and it doesn’t help that her magicae is unpredictable and out of her control. Her new life is dangerous, and it’s imperative that Zoe figures out what type of witch she is and that she learns how to harness her magicae before she gets hurt.
Luckily, men from her past are there to help with the transition, and they’re more than willing to protect Zoe whilst she learns to defend herself. But when they’re keeping secrets too, how will she ever know what’s real and who she can trust?