In a more alert state, she'd be significantly more attuned to the fact that she's being observed--which has more to do with her own hyper-vigilant wariness than the idea that it's noticeable to most people, because it isn't. For now, she feels like something's on the tip of her tongue, or the back of her mind, or some turn of phrase used to mean close but not quite. She rubs carefully at one eye with her knuckles, in a fairly pointless attempt at salvaging some of her eyeliner.

"Kind of like how people say you can tell the truth about somebody by how they treat their so-called "lessers", but bigger?"

Or whatever it is they actually say. She doesn't remember where she picked that one up. On the tail end of the question, she actually glances half at Mycroft; mostly she watches the scenery, in such a way that suggests she's accustomed to keeping an eye on her location for any unexpected new elements. It's not something she does entirely consciously.