This isn't codependency according to my understanding of the term. What it is, as so well said above, is an overpowering sense of empathy. This is no problem in my books. You are caring. However, if you are dependent upon your child for your own emotional needs that I would say is a problem. It is hard not to live vicariously through them. It is possible you may need to practise some detachment from your daughter - let her go to some degree and have some trust she will be okay. Remember being a best friend is not being a parent.