What you want to do is pretty noble but you still have to be careful. Sometimes, people can use their "poor background" for manipulation. Just because she had an unfortunate past doesn't mean she is a good person. In fact, considering her background, chances are she is ONLY with you because of the financial benefits you are providing for her. If you really want to help her and you can afford it, sure, go ahead and help her BUT be very careful. Out of desperation, she might steal from you, damage your credit, or even put you in jail. Crimes are easier to commit with people closer to you because you can access their information easier.
Also, admit it. Your intentions are good but you have your own selfish motivations. There are so many unfortunate people in this world (African children starving, etc), why invest all your money on her? Be honest, you want her to see you as her savior and marry her eventually, right? Just don't get bitter (or go crazy) later if she leaves for another man and show no gratitude after all the things you did for her. Do an honest assessment of yourself. If you are sure you want to do all this for this woman and even if you get nothing in return (she leaves you for another man and show no gratitude), you still won't regret it, then go ahead with your plan.