[She's pleased he looks down at the paper, because it means she can successfully hide her smile without him knowing it. Rosalind busies herself with her drink, and then, when she thinks she can keep her expression under reasonable control:]

My mother was never very fond of my spending too much time in the library. When she inevitably kicked me out, I'd grab my physics books and climb a tree, and do the precise same thing anyway. Though I suppose I at least got some fresh air while I was at it.