I don't really get this one shot at all. Which are the girls is the mother of the baby. Genetically, it could be either as the dark haired woman could have a recessive allele of blonde hair and so could the father of the baby to produce blond/light coloured baby. However, the interaction between the light haired and the guy suggests that she is most likely the mother of the child. Also, the baby does look like her, but, you can't really tell in a manga.
So, if the blond/light haired woman is the mother of the child and she is saying "She is still my dear friend." This could mean various things. First, she is looking at the picture with a sense of nostalgia and is crying happy tears that they are still friends. In this scenario, she is maybe thinking that what she has in life and it is enough for her, which means that this is actually a happy story.
Or we could say this story is about unrequited love and both girls maybe missed the opportunity to love each other. The light haired women moved on with a baby as we are going with the theory that she is the mother and she is crying that they are friends as she still has the dark haired women in her life.
For me, I didn't feel sad because it was too vague of a story. There are too many interpretations that this story could mean. In my opinion we didn't get enough of a story for me to feel emotionally invested as a one shot. It was decent enough.
