There have been a lot of these threads on this forum since I joined it. Most of them have been about how many times the OP has tried talking to their SO about money, and how nothing ever changes. If you have one conversation, and the person actually makes some changes, then they have the potential to really get on board with things. It seems that this frugal lifestyle is either for a person, or its absolutely not. I have always liked the sound of it, but until a friend of mine asked point blank waht I earned then upon learning my salaray he put his big scary biker finger in my face and coughed "You should be saving more!" in my face, well, that's when I woke up.
If your conversation turned on a lightbulb for your girlfriend, that is amazing and wonderful... if it hasn't, and she isn't now asking YOU about how to get on board, that's when I'd suggest you accept the reality that you won't ever be on the same page and to keep your finances and spending habits separate forever, lol. I say "lol", but I'm also serious.
Most people want to see their SO's potential and they waste a lot of time not seeing how they truly are, right now, today. Learning WHY someone spends a lot of money can help you invision whether or not they have it in them to adjust to a plan for the future or not. Some spend because their income is new to them and they are thoroughly enjoying that, like I was, some are spending because they have an emotional block on looking to the future and how to plan for it. I wouldn't knock anyone for either mindset, I would accept it and then figure out what YOU feel you need to do.
Usually these threads end the same way... the OP saves face and claims things have changed, then never posts about it again, or they argue with the answers... or like one of them, the SO actually joined the forum and defended her wonky spending habits as emotional support for her past. Yeah, good luck to that couple. And really, good luck to you, this is a good waking up point for you. So keep her or don't, either way, be real about it.