Within Keima's hypothesis and combined with your comment, it is a sure thing. If Ayumi was just slightly miffed the the way Chihiro is slightly miffed and without knowing why, she wouldn't act the way she did in this chapter.
Ayumi has shown interest in Keima previously, multiple times. Her "nostalgic romance feelings" have thus far been expressed through hanging around him, watching him, and subtly (yet clumsily) interfering with other girls (the sports festival). She's been nicer to him overall. Chihiro hasn't changed much (though the coffee/tea is a step up). But now we have Ayumi booting him across the room as hard as she can. That's far from her recent pattern. It's the opposite of what we've seen.
Jealous much? She remembers, there's no way she doesn't.