"Thank you very much." Sinead nodded as the shopkeeper bustled away to the shelves, picking up one of the quills displayed on the counter and examining it as she waited. It seemed that wasn't to be her only passtime, though, as while she was distracted somebody walked straight into her back. She looked up with startled and accusing eyes, only to see a baby-faced kid who didn't appear any older than her, though she didn't recognise him from any of her classes, so maybe he was.
"Uh, don't worry about it," she said, somewhat taken aback by his abject apology. It was kind of difficult to stay annoyed in the face of all that. "Are... you okay?" He obviously hadn't seen her, which kind of made her wonder how he could have been quite so blind. She was literally just standing right there.

As she continued to do so, the shopkeeper reemerged from between the shelves, proffering the promised quill as well as a little stack of notebooks. Sinead smiled somewhat awkwardly at the boy beside her, hoping he didn't think she was just ignoring him, and leaned over the counter to scrutinise the different notebooks. Alohomora was all well and good, but she went to a school where literally everyone was taught that spell... so she might be better off with a padlocked book.
"I'll take this one, please," she decided, sliding one in a dark green colour out of the stack. House colours were pretty hard to overturn; she felt like everything she owned was green now.