"Accidental Demons", by Clare Edge. It won't be available until September 17th, but I'm already anticipating the read. It's a middle grade story, tagged as LGBT on Goodreads.
As if a recent diagnosis of diabetes wasn't difficult enough, Bernadette has a problem: she's also a witch-in-training. Now, every time she pricks her finger to test her blood sugar, she accidentally summons a low-level demon. Fortunately, her sister, Maeve, is there to help her clean up the aftermath. But, when their plan to use a demon as a blood sugar monitor goes awry, the consequences could shake the magical world to its foundations....