The protagonist is quite colorful. She is an adorable serial widow. I liked her despite her being 200% sociopath.
What is interesting about this game is that the player is presented with contradicting facts. No matter who will be chosen as the killer suggested theory about murder won't explain everything. So it shouldn't be big surprise here that you can paint as the murderer practically anyone. It's well known fact in logic that you can derrive anything from contradiction. It's basically what the protagonist does. She highlights facts good for her theory and ignores the rest.
For this reason it doesn't make much sense to think about "Who is the real murder?". Without aditional information removing ambiguities there is no way to tell.