I went through a similar situation with my daughter.
You can make a difference, and are, in your grandchild's life. Providing stability and a loving environment. Focus on that. As you have found, you can't control what your daughter does. But you can control your influence on your grandchild, and know that they are being well cared for, by you.
The child is lucky to have you, don't miss the precious moments. Sometimes we, as grandparents have to go through a lot.