I like this photo. I enjoy looking at this scene. I think that is important when taking a picture for a greeting card. I like grain too. I think that it can add character to a photo. IMO, grain can create a feeling or mood with a photo that seems boring otherwise. In your photo the little girl (darling BTW), is picking up shells. She is gathering objects maybe for her collection. This action does not say friendship to me or missing you or even thinking of you. Maybe other voters felt the same way and that is what resulted in a 5.4 score.
Your picture is very cute and different (added grain and desaturation) which sometimes is not liked by the majority voters. This probably wasn't what they had in mind for a greeting card. It is not easy to appeal to the masses. I have a very hard time myself and have made up my mind to take pictures that appeal to me and me alone. If I do well in a challenge I am thrilled, but if not it is not the end of the world. Overall, I think that this is a cute picture and I hope the best for you. I see a ribbon in the near future. Your work is excellent and it is just a matter of time.