"Oh, it's alright," Hermione assures her instantly, smiling still as she approaches the counter. She glances toward the cauldron then focuses on Lily once again.

"I'm just looking for a bit of Knotgrass," she explains. Which just happens to be the most common ingredient in the potion but she doesn't want to spook Lily or give herself away too quickly. Just to be safe.

"Are you Lily Evans?" She knows the answer of course, but it's polite to ask.