I told my girlfriend today...in our previous discussions she seemed like she wanted me to leave. However, this time, she flipped out on me...arguing in line at a sandwich shop, saying I am a liar...I am running away from her, etc. Now I'm even more torn that I've made the decision.
She may need (more) time to get used to the idea. Or it may strain the relationship too much. Either way, I think it's up to both of you to decide how to handle this - you've chosen this job, you can choose to end the relationship over the distance or work to make the relationship last despite it. If she's yelling at you and calling you a liar, I don't think that's the best reaction.
I'm in your girlfriend's shoes at the moment - my bf may be moving to the US for a year+ for work. I don't want him to go, obviously, and he doesn't really want to be there (other than the work opportunity), but I'm leaving it up to him to decide what's best for him. If he were to decide to stay/go based on the relationship, as others have noted, that would likely kill the relationship due to possible resentment, etc. So he has to decide on its own merits. I do bug him from time to time for updates as to whether he's closer to making a decision, but I would never claim he lied to me if he decided to go.
Ultimately, it's up to you and your girlfriend to work out (or not). She could have a valid claim on the lying if you've been promising to move closer for years and are now moving (much) further away. That said, life happens, things change. It doesn't sound like you avoided moving because of her. If you've handled being a small distance apart for 3 years, you can handle more. Or not. It just depends on how the two of you act/react to events.