One thing to always remember: Things can get a lot less fun when they become a job.
I have a thread somewhere in here. I'm one that left. I'm finding that in my current job I have much less time at home than I ever did at the airlines. Working 60+ hours a week will have that effect. I'll never do the regional airline thing again, but I'm seriously considering returning to flying for a living. There are a ton of jobs flying airplanes that have nothing to do with the airlines.
While some here are reading you the riot act about the girlfriend, I think they have some valid points. Never let someone else dictate your course. Especially in your 20s. Support, yes. Question, yes. Dictate, no. I didn't marry until I was in my 30s, and I'm glad I didn't. Honestly, I would have never even dated my wife in my 20s. I probably also wouldn't have a marriage and family right now, let alone a happy and supportive marriage.
Bottom line: you gotta do what's best for you. All you can do is make an informed decision and go for it. Whos to say that you decide to go the engineering route, the economy goes TU and you're out of work for years? I think the current state of affairs is as good for someone getting into aviation as its ever been in my 20 years of it, but its always a crap shoot.