We probably need some clarification about what your grandmother meant when she said "I don't think I'll ever be able to forgive you for this." I assume that's a direct quote. My mom worries about me when I'm on the road but she says stuff like "I'll be worried sick about you." Somebody who says something like "It would kill me if I heard that you were hurt" might be inordinately concerned about your safety, but that's still a pure expression of concern about you and your well being. "I can't forgive you for this" is different. If you don't know what your grandmother meant by that, you should ask her and talk it through.