MartyMomma:
Avoid. There's nothing to be gained by attacking it. She made the plans. You stated she had NO intention of attending parties/festivities.
While it's sweet of you to want to make them a plate, I wouldn't. It's not like could eat it in the car and once they get to the airport open food like that might not get past security.
Your sister is being VERY inconsiderate and acting like a spoiled brat.
She might be upset that the festivities are the day that she is leaving and is worried about being late for the airport and since she might be stressing over the death of her MIL as well as a 22 hour plane ride she might not have the right words to state why she is upset. Therefore her tizzy.
You want to avoid drama and like things low-key? Okay - don't deal with it. Don't make her a plate and ensure that your husband is there in time to drive her and her family so they are not late.