Don was off doing his morning things -- breakfast, then a smoke somewhere on the train -- and Lily was sort of tracking down her friends. She had a sneaking suspicion that something was going on between Tris and Marvel that she ought to be aware of but wasn't because of her own personal drama. So she wanted to find them and drag it out of one of them, and she thought she could manage that just fine.
She was, in the process of this, avoiding her father. As far as she was aware, he hadn't yet apologized to Don, and she was still (yes, still) mad about the whole situation. Things between her and Don were just fine -- lucky for Harry. If things had gone sour because of her father ... well, she wouldn't be speaking to him, and she'd be out a ... whatever Don was. Boyfriend sort, even if that was too immature a word for what he was to her.
Reasoning that Tris might be in the observation car (he was trying to work on something so people could look at the scenery and not go dizzy), she tried there. She didn't find a Tristan, but she did find one of their future professors playing with the herb garden. She was half inclined to warn him that Snape stopped by there sometimes, but that didn't seem like much of a greeting.
Still, it was awkward. She knew him as a much older family friend who'd played an important part in the war -- and her herbology professor. Seeing him here, her age, was ... weird. Granted, he had no cause to know anything about her, which was fine. She'd managed to net enough detentions in his class that it was probably just as well he didn't know her yet.
"H'lo," she greeted him casually, pausing to regard him and the plants while trying not to look out the window.