It feels like she does try to say she was tripped up by the main character or that she was shoved, and she is crying, there are people whispering in the background as if they hadn't been watching the two dance, and one noble knight goes on to yell at the princess, but her aide and dancing partner steps in to defend her.
Not only that, but the king appears too and going by the art, it seems he came in time to watch everything and he's pissed off, he threathens the knight yelling at his daughter and glares at the "heroine" before picking the main character and spending time with her, it seems like he also takes the time to say that she did not do anything.
Basically, the "heroine" tries to make her sister look like a jerk, some people take the chance to attack the seemingly useless princess, and her aide and father pretty much tell them to shut the fuck up, also, the main character apparently begs her dad to not punish anyone, and there is one moment where it seems like her dad becomes speechless at her cuteness.
Again, i can't read what anyone is saying, i am just going by what the art shows, but it's clear that the plans of the "heroine" royally fail and she and the guy that supported her come out looking like idiots.