It's because she is random at what she feels bad about. She don't care about going with the crown Prince in the place of Eris and humiliate her this way but somehow wearing the same dress and being humiliated herself make her broke down. Like, no sis. It's should be the reverse. You are not a noble so should'nt care about your reputation and what you are wearing. It's about geing the crown prince's escort that you should be guilt over in the first place.

I actually a bit mad at Helena. I know that she can't do anything cause she is just a maid but I don't know maybe because I watch this story at Eris pov cause I feel like she should at least defend when cp say that Eris hurt Helena but at the same time I also feel bad at Helena. arghhh I just don't know cause the spoiler just make me feel like mc story is just so sad that it make me A little bit angry at Helena.