"Ahh, so you're a visitor to that library then," she said, realizing that he couldn't be talking about his library at home, if he was talking plural. And really, she was making this too complicated in her head. "I'm not sure anyone can ever own enough books. I'm pretty sure that's an unquantifiable amount."
She laughed, thinking that dramatic fit Severus very well. Though she was confused as to Al's interest, she had no problem talking about Severus, and took a bit of food first so she could get her thoughts in order.
"He was brilliant, and difficult to love," she said finally. "But he was also the sweetest and most loyal friend I ever had." She knew that now, looking back at their relationship. "He scared me, with his obsession with the Dark Arts, and how easy it would have been to follow him." She regretted now that she hadn't fought harder for their friendship, hadn't given up on Severus so easily.
"He was the first friend I ever had, and taught me everything I knew about the Wizarding World." She sighed, and looked back at Al. "I loved him, even though he made it difficult at times, and despite everything if you asked me who my best friend is, I'd say without hesitation Severus Snape." She realized that she'd maybe given too much information, and strayed from the question, and shot Al an apologetic look.
"Sorry, I tend to ramble a lot. Dad used to hold up five fingers, as a sign that he needed five minutes to process through what I'd said."