Without any prompt at all, my stepdad starts raising his voice at us, telling us to quit looking upset, and we can't control nature, get over it, and storms off screaming 'God Damn!'. My mom turns to my girlfriend, and says "Why are you looking upset, a delayed flight isn't that big of a deal.", to which she replies: "I'm sorry, I'm upset because I just got yelled at by your husband."
My Stepdad walks back into the conversation, and says: "That was hardly yelling! You will know when I am yelling!". She promptly replied saying: "I'm sorry, I meant to say I was getting upset because we were both getting chastized". My stepdad stormed off, and we went back home (to my parents place)
If this is what happened, then I think it is your father who owes your GF an apology. Although based on your post, he is unlikely to give it. Your GF used a beautiful "I statement" to explain her upset. She used bad judgement in how she expressed it, tho. I suspect her statement came across as judgemental to your parents. In her shoes, I think I would have just excused myself for a moment and let them consider their behaviour without saying anything overt (personally, I would have found it amusing to see him lose it over something so trivial, but I'm a different personality). Also, she may be a bit too sensitive to deal with your family if they tend to be more on the fiery side, and she more reserved. Conflict style is very important in a relationship. I hope you are compatible this way or you will end up having problems dealing with an over-sensitive partner.
Anyway, its clear there is more going on here than your parents not liking your GF. Sounds like your dad and mom have issues.
Second thoughts can generally be amended with judicious action; injudicious actions can seldom be recovered with second thoughts.
--Cyteen by C.J.Cherryh