She shrugs, cause - Wayne Manor is big. She doesn't think she's lost, exactly, so much as exploring and creating her own mental map of the place for later. "Alfred said I should maybe go find you cause he had some things to do and he wouldn't mind the company but they might be boring." It was, actually, a choice rather than the kind brush-off Tim took it to be, but it may take some time for her to realize stuff like that.