Regarding the "I don't feel pretty" comment at the Dec 23 party: I've seen mention in several books that JonBenet had not wanted to change clothes for the party. Patsy had insisted, so JonBenet put on a black velvet dress with short sleeves. Perhaps JonBenet "didn't feel pretty" because she'd been forced to change her clothes? Or perhaps during the mother-daughter dispute, Patsy said something along the lines of "well, don't get ugly about it!"
I well remember at that age all it took was having to wear some god-awful froo-froo dress I didn't like in the first place and bingo! I felt "ugly" because I stood out.
(This was back in the early '70's. Mom was dressing me like it was 1962, not 1972!)
Bottom line, it could well have been the clothing issue.