Responsibility, no. But OP had literally no other plans or responsibilitys. He choose to sit back and watch his GF stress, giving nothing but a measley "Sorry about this" and drink and sleep in instead of offering assistance. It's not even a big favor, it's an hour and half of his time to give her a peace of mind. Partners should WANT to help eachother like that. Partners should HATE seeing eachother upset and stressed at least enough to make minimal effort to help.

GF even said she wouldn't have taken him up on the offer - out of consideration for him. Which I believe but simply saying that shows and cares for his feelings. OP is a selfish brat.