She goes to her and Sherlock's room to drop off her belongings and let Euterpe out.
"Expecto patronum!" Bella insists to her wand, and nothing. She tries her other wand. Nothing.
That gets her mist. Weird.
"You are so much better at this than me. I wonder if it's just because you're older, the book did say people don't usually learn it early. Maybe I'll go find Tony and see if she wants to come try." Sherlock, of course, is asleep, but she can show him between when she gets back to their room and when she goes to sleep if he's curious.
"Ooh," comments Bella, and in she goes to Tony's room, at which she knocks the perfunctory knock of someone who during the school year crashes there at least once weekly.
"Me and Feral are trying a spell I found in a book called the Patronus, do you want to try?"
"It's supposed to make a spirit guardian animal thingy that's good against some Dark creatures. The book says it's really advanced and I haven't gotten anything better than mist but when I left Feral his kind of had limbs."
"C'mon." Bella shows her out to where Feral is, and shows her the copied spell description from her notes on the way.
"Yeah, I didn't even get that on the first try." Bella concentrates as hard as she can. "Expecto patronum!"
"He has a head start," Bella says, shaking her wand as though to dislodge a blockage and trying again. Mist, nothing but mist.
She tries again. Her blob darts in a little circle before dissipating.