Kat totally could tell James's interest in Neville, her eyes went from James to Hermione as they talked, and once turned to Neville, who was not in the mood for it. She knew she didn't need to stay but she also knew that if she left the conversation would turn really awkward for Neville, so she decided not to follow Hermione.

"Save me a seat as well!" she told Hermione, as she looked away to seat next to Harry and Liam, that wouldn't be great as well.

"Wow, flying, huh?" she started, just the thought of doing that just with a broom slightly frightened her, "I've never done that before" then remembered all the times she was in a plane "Well, not on a broomstick...I hope you're a good teacher" she told James.