Help me please! My girlfriend wastes so much money and is sometimes so negative.?

When she starts to complain about something, point out the positive in it. Like if she complains about a certain restaurant, point out that they have awesome desserts or a really cool atmosphere. As far as the wasting money, that's just something that couples need to figure out together - some people were raised not really caring if they can save a lot of money based on their choices and other people were raised very frugal. These aren't huge issues now, but if you don't come to an agreement they can turn into big issues.