So you met up with someone at a cafe and didn't order a panini like you normally would, your friend asked why, and you told her in your words because 'you stuffed your face all day' the day before, so she asked what it was you ate in this apparent foodathon that meant you 'couldn't possibly eat anything' for lunch the day after.
you are listing a large breakfast (fine if you are used to that sort of thing), a small lunch (fine), a HALF portion of pineapple slices as a snack (fine), and a small dinner (fine), you felt full when you went to bed because you ate the extra children's portion (too much), not because you had stuffed your face "all day" ..
So bear in mind this is the NEXT DAY and you are saying the reason you don't want any lunch is because you stuffed your face the day before, even though you didn't actually stuff your face at all.. so why not just say you weren't hungry and leave it at that?
By saying you couldn't possibly eat because you ate food the day before, you are making her feel guilty for having a perfectly normal appetite, you do sound like one of those annoying people who have lost weight who can't just be around food anymore without passing comment, I don't think the competitive under-eater comment was misplaced to be fair, you had no reason to tell her any of that, you were just using it as a point scoring exercise.