Thanks so much for playing my game! Sorry it took so long for me to respond here.
=== SPOILERS BELOW ===
That one's more of a mistake on my part. I leave it assumed that if Angela is the killer, then she is the person in the photograph. Maybe I spell it out in an optional piece of dialogue somewhere. In either case, you didn't miss anything. I should have made the plot point more clear. I'm glad you enjoyed everything else!