You could ask the parents if you can take responsibility for your goddaughter’s Catholic education, reminding them that you promised to assist them in providing a Catholic education for your goddaughter. But if they refuse, you cannot educate your goddaughter in the Catholic faith against their will. At that point, what you can do is to pray for this family, offer up any sufferings and sacrifices that come your way for their conversion, and let them know that you stand ready to do your duty as a godmother to this child should they ever change their mind. And, once your goddaughter grows up and, as an adult, is mature enough to consider Catholicism on her own, you might approach her and ask if she wants to learn about the faith into which she was baptized as a baby.