How about I agree with my girlfriend's cousin and not her?
That sounds reasonable but what makes you agree with your girlfriend's cousin?
Because her cousin's job is way more important than my girlfriend's
While you care about your girlfriend, that doesn't mean that the two of you must agree on every issue. If this is a sensitive topic for her, be respectful while sharing your opinion.
I'm not trying to be disrespectful towards my girlfriend but I really believe that my argument has points.
Obviously, you have already weighed the pros and cons in your decision, so I think it's logical to just go with your guts on this one. It's not like you have to take your girlfriend's side every time. You have got to do what you think is right, and I am sure your girlfriend understands.