Okay so basically my gf goes to University and can only go abroad for a holiday with me on certain dates, since the flight companies are aware of this, flights go up roughly $600 return. I don't like that. 

If I left a couple days earlier (and a day later on the way back) than my GF, I'd be able to get a return flight for $600 less. She can't change her dates so she'll have to fly by herself. 

She's really mad at me and is telling me I don't care about her, when I do, but it's a 5-6 hour flight each way, surely that doesn't compare to saving myself $600. 

So, AITA?