I'm just now getting around to posting this, but I really wish Betty's family would be more understanding of what she has to do for work. A job comes with responsibilities, and her responsibilities are pretty enormous. They should also understand that if Betty makes a big mistake, it's up to her to fix it.
However, I do think Betty should have gone right to her sister's opening after getting the dress back. It was crappy of her to stay at the party, even though it was a huge honor to be invited.