If you're serious about becoming a professional pilot, you'll need to forget about a girlfreid or friends for a year or two because to even finish flight training requires a lot of dedication and effort. Girlfriends are always a distraction because they will never really understand what it takes, and so you'll either start but not finish because they'll complain you're not spending enough time with them (you'll know about this when doing ATPL theory) or you'll start, barely finish but still be stuck. Because as a freshly minted pilot yearning for experience you'll need to be able to move anywhere for that first flying job. A girlfriend, as supportive as she might be, will still make it hard for you to make a decision and you'll eventually just wait for that perfect dream airline job close to home and close to the girlfriend which will probably never materialize.
You need to really want this and be ready to sacrifice everything, otherwise it's not for you.
I wholeheartedly disagree.
I met a girl two months before I started my PPL. She was an exchange student and I didn't expect the relationship to last beyond her program. I completed the PPL through an intense, 6-week course, and I was straight up with her that I would be focused on my training. When finished, we continued dating for the remainder of her exchange. When that came to an end, I decided to travel the 13,800 km to her country for a visit. That visit turned into a move, and I completed my professional licenses in her country. She never complained once when I had to hunker down to study, or be gone almost every weekend, or go to places in her country she'd only ever read about. She never complained because we talked ahead of time about the financial and time demands the next course would require of me. She never complained when I swapped jobs in those first few years either because I was upfront about how that change would help my career and our future. Then when it came time to build multi-time for the airlines, it was she that pushed for the move out of her country and back to mine. We moved overseas (again), this time into the high arctic to another town both of us had only seen in textbooks. 7 years later when it came time to move companies again, she made arrangements with her company to continue working, despite moving 1,700 km away. When the airlines began hiring again, she didn't blink when I said I'd be commuting clear across the country for up to 20 days a month.
We just celebrated our 24th wedding anniversary. She was never a distraction, she often got what this industry requires before I did, and she never held me back from completing the exams, tests, or moves that I needed to do.
Now, not all partners will be like this. I know lots of guys and gals whose boyfriends and girlfriends couldn't deal with the demands. But the same goes for doctor and lawyer friends of mine. Any profession has its unique difficulties. It is not on our partners to understand those difficulties on their own. You have to communicate the financial and time demands this profession requires to get into it. Otherwise, it's not the profession they don't understand, it's you. It's also a two-way street. There are opportunities I've passed on because that was a red line for my wife. Do I miss the chance of not going into the Air Force or moving to fly in some tropical island, yes. But that ensured my relationship remained intact.
Where I do slightly agree is that you will have to sacrifice. There are no jobs, or at least none that readily lead to the airlines, that allow you to have your cake and eat it too. If you want to get to the airlines quickly, you will have to sacrifice time with friends and family. That doesn't mean all the time, but it does mean more than you probably think. If you're not willing to sacrifice time with family, then it means you won't be flying as much, sacrificing your career path. It's a delicate balance that you're more than likely going to strike wrong more often than you strike right. But communication is key.
For example, I was a standards pilot for my previous aircraft type. That means I drove a desk far more than I drove airplanes. I built most of the training programs, taught a little, and did more than a few check rides in a month. This all kept me home and pretty much on a 9-5, Monday to Friday schedule and was a mentally stimulating job. It also allowed me to be home for the vast majority of my sons first 7 years. But, I went from flying 700 hours a year to I believe my best in the office was 120 hours. The worst was 50 hours. There were more than a few times where I'd be sitting at my desk to realize I'd not flown in 80 or 90 days, and instead of going flying, I'd take another standards pilot down to our simulator to bash out the required takeoffs and landings, and be good for another 90 days. All because I had too much work to leave the office. So while my family life was amazing, my career took a different turn and flying definately took a back seat. While I still gained seniority, I passed on several opportunities to move over to the jet, which has affected my long term earnings potential - by almost a million dollars.
When I did swap to our jet, I came back to the line. I now get blocked between 9 to 16 days a month, depending on how I bid. If I get a 9-day month, those are all heavy credit 1-days where I will see my wife and son for maybe 15 minutes in the morning. Those are great months though, because I'll have the rest of the month off to be with them. If it's nearing 16-days a month, that'll be low to medium credit 3, 4, or 5-day pairings. Best case, it's an easy pairing with lots of time to call home. However, there is probably 1 pairing every month and a half or so where, because of time zone differences, I don't get a chance to call home for the entire time I'm gone. Those suck. But, I make it a point that when I'm home, I'm home. That is family time. I do what I need to while they're at work and school, but as soon as they're home, I'm theirs. I know lots of other guys and gals I fly with have the same mentality, and it makes family time more meaningful than it might otherwise be.
So no, you do not have to be ready to sacrifice everything, or forget about relationships during your schooling, or cut yourself off from the rest of humanity to chase a dream. Whatever challenges you and your girlfriend have already overcome during your engineering degrees will be transferable to your aviation path. Just with maybe a little more time away from home. Just be open and honest, listen to what she has to say and be willing to not take the first opportunity. There is more to life than flying, and some people don't get that until it's much too late.