Theo nodded by way of acknowledgement. He was about to continue walking when she asked him a direct question, which he could hardly ignore. It's not that he detested her, although her chirpiness might have often caused him annoyance, but a mixture of not wanting to interact with most people and reminders of the past helped him keep his distance. Also, his complete belief, despite how misguided it might be, as being able to cope with everything on his own helped immensely.
"Fine" he replied, expressionless. He contemplated sitting down. He was tired after all from the walking but then thought better of it. If she'd been a Slytherin, he might very well have. Instead, he continued standing. "You?" he asked, more out of politeness than concern.