yeah, just played this and got it "wrong" even though i'd provided what was an acceptable solution in my eyes..
it is due to the way that the meaning of "next to" changes between rule 2 and rule 3.
in rule 2 "next to" is applied to the
people (the person next to her)
in rule 3, it is applied to the
plates (the plates are next to each other)
however, i don't think it's logical that "next to" for people counts for 'around the corner', and next to for plates (when they are arranged like ::

doesn't count. i see the U-shape argument, but it falls down, because on rule 3, we're no longer talking about the people's positioning - we're talking about the plates positioning - which are in more of a straight 2x3 grid.
if rule 3 was changed to "one couple had the banana split and ham" - it would work, or "the banana split and ham were on the same side of the table".. or some other way of expressing this. i think 'next to' is too vague when we've already been allowed to use 'next to' in a loose-ish way for rule 2.
oh well! enjoying this game a lot other than this!