Quick short review:

Story - 7:
Laura's father dies, and Irene's mother dies. Their remaining parents meet and get married, but because it was so soon after her mother's death, Irene cannot accept her father, Laura or her new mother.
Pretty basic story, but a good premise for a one-shot.

Art - 7:
General shoujo art. An upside is that it's not super sparkly and the characters don't have yelling matches with dialogue all over the place, making the pages look cluttered.

Character - 6:
Enough backstory to understand why they act the way they do. But obviously, since it's a one-shot, you can't expect much.

Enjoyment - 8:
There was a pretty obvious twist, but it was good to see how things ended up.

Overall - 7:
Suitable score for a one-shot that wasn't all conventional.