It sounds as though you're concerned about how the differences in your approaches to money will play out in your joint future.
This is a valid concern.
I predict that continuing to tell her all the time that she needs to save more, while subsidizing her lifestyle with your earnings, will get you exactly the same money dynamic you have today.
If you want different results, you have to do something different.
No one here knows your relationship like you do. Only you know what you can tolerate, what she can tolerate, and how money plays into the totality of your relationship. However, I suggest that if you don't want her to expect you to subsidize her lifestyle with money you have earmarked for savings, you should make that abundantly clear. Also, once you set a boundary, if you let it slide, you will teach her that you're not serious when you tell her about your boundaries. If you do set boundaries and expectations differently than up till now, and you're consistent in not giving in, she may push back. That's when you will need to make clear what you're aiming for in your life, whatever that is. The thread referenced above will give you some help in how to express that.
I'm not in the same situation as you, but my husband and I do have different approaches to money. He pretty much only makes enough money to cover his bills and the things he and I have agreed he'll provide. He has almost no stash. Because he recently had some lumpy expenses, he was cash flow negative last year, and he's using his paltry retirement account as a buffer. So he and I had a frank talk about expectations and how he can earn more (which should be relatively easy for him) so that this trend doesn't continue. Happily for me, I feel like I'm doing what I can to head off any problems (meaning any requests for help from me) before they occur. In contrast, you've already taught your girlfriend that when she wants a new car, you'll buy it for her, and that she can still spend everything she makes on going out. You can reset this expectation, but it may not be easy. I would say, be nice, but make clear what you want and what you're willing to do, but also what you're NOT willing to do -- any more. The exception to this is if you're actually willing to keep doing it. And you may be. Is this a dealbreaker for you? That's what you have to decide.
Also, beware. If your income goes up, she may expect you to spend more of it on her cars, clothes, trips, whatever. Did her parents provide all these things to her growing up? Did they expect her to make her own money? Whatever she grew up with, she may expect the same from you. Now, it's perfectly reasonable to expect that as a partnership, your making more money will help both of you, not just you. But the two of you should work out exactly what that means.
This is kind of rambling, so I'll stop. Good luck to you. We're rooting for you.
