What do I do about her? She deserves better?

She is old enough to make her own decisions, and it seems like she is very happy with you so why try push her away? If she thought that being with you was holding her back i'm sure she wouldn't be so happy, Your both still young so have fun and enjoy being with each other. You never know staying with you might be the best thing that will happen to both of you. If your really worried about it, discuss it with her.