You are not responsible of choices made by other people so the guilt that you have been burdening yourself with was never yours to begin with.
Guilt is a mind mechanic whose purpose is to make us feel uncomfortable with choices whose results don't please us in order to make sure that we act to heal the wounds caused and choose better next time, this is how we acquire wisdom because no one is born wise, we become wise by learning from mistakes.
This is why guilt exists, because the purpose of a mind is to learn and acquire wisdom so mind comes with many mechanics such as thoughts, ideas, imagination, emotions and such as ways to achieve this purpose of learning and acquiring wisdom.
Therefore, feeling guilt for choices which were not yours, that you couldn't and still can't do anything about is pointless because punishing yourself is unfair if you didn't do anything which calls for punishment and pointless if it doesn't teach you to be better.
I don't feel guilty for playing your game even if its ending is definitely not what I wanted. Because there is no other ending. What is the point of blaming myself for reaching a bad ending if it is the only ending reachable? You know this already because you made Jo spell it out: "You can't make any choice for me." To put it in another way: "I make my own choices." So Jo acknowledges that she is the only one making her choices. Which implies that she is the only one responsible of her choices.
But Jo is hypocritical because right after she made me feel helpless by stating that I can't do anything to change her mind, she put the blame on me by stating that I am the one who talked about "blood" so I am the one who gave her the idea of solving her issues in a bloody way.
Well, while it is true that I indeed talked about blood, what I said precisely is "She is your sister, it's in your blood.". Which is far away from "Poison your sister's blood.".
This interpretation of the word "blood" is her own, not mine. She already saw her sister as a nuisance to get rid of and believed that the world would be better without her long before I even got in touch with her, she was just waiting for a scapegoat to burden with her own guilt, someone to put the blame on and take responsibility for her.
It is the same as why people have imagined the Devil and demons, some embodiment and source of evil to put the blame on for all harmful desires, some manipulative and nefarious influences from outside and insidious voices in our hearts who tempt us, pure souls, to do questionable things, because most people are hypocritical, they rather blame outside influences rather that taking responsibility for their own desires, anything to not acknowledge that the evil comes from inside.
And there are people whose ego is so big that they take responsibility for everything that happens around them no matter who actually did the deed, they blame themselves when some people harm some other people and themselves as if they could have done something to prevent it from happening, as if they had control over other people lifes.
In your game, I have absolutely no control over Jo, I might have a few options to choose from to talk with her, which involve different replies from her and different paths to follow, but in the end, my choices don't matter to her because her mind was made up from the beginning and no matter what I tell her, all paths lead to the same ending, Jo wanted to get rid of what she believed was the cause of her unhappiness all along, my involvement was only to be there to put the blame on, my role was to be a scapegoat.
If I wasn't there, if I didn't interact with her in the first place, if I hadn't been the scapegoat that she needed to act on her harmful desires, then she wouldn't have acted and it would have been for the best, that's what you think, that's why you gave me the option to not help her from the beginning then claimed that I did something good.
I don't regret having played your game, I don't regret having choosed to involve myself with Jo, I don't regret my choices, because I did my best, no matter the result, I couldn't have done better than what I did so I am actually satisfied with myself, I don't take responsibility for what she did, because this was not my will, I never had any control over her from the beginning.
To live with no regret is not to succeed everytime, it is to do your best no matter the results. ;-)
If I hadn't chose to help her, if I hadn't involved myself with her, then what? She wouldn't have wanted to get rid of her sister? Her innocent sister would be safe if I had minded my own business? I don't think so. Her family was dysfunctionnal from the beginning, with or without me, I didn't change anything, I merely involved myself, trying to help, trying to change things, but I couldn't change anything, I didn't cause the changes, I merely was a helpless spectator of the drama all along, with no control over the events. So why should I regret having choosed to try to help her if my choices never mattered from the beginning?
I am actually the only person involved in this experience who is not guilty of anything.
Me and the sick sister of course.
Let's analyse this experience, shall we?
I have been a spectator of the events all along, my involvement never meant anything from the beginning so I didn't cause anything that happened, therefore I am (and you are since it is your story) not guilty.
The sick sister didn't choose to be sick nor did she evict her father from their house nor did she request that her mother pay more attention to her than to her healthy sister so she is not guilty.
After the grandmother died, the grandfather became obssessed with their chicks, likely because they remind him of her who is no more, and is guilty of having chosen to stuck himself into his own memories of past events and a person who doesn't need him anymore instead of paying attention to current events and people who need him right now.
The father is guilty of having choosed to run away from his problems instead of staying and facing them with his family.
The mother is guilty of having paid attention only to physical health and missed mental health. Indeed, she focused her attention and care on her sick daughter because she thought she needed it more than her healthy daughter, completely missing that her healthy daughter was becoming sick too, but in her mind, because of feeling neglected. When you see 2 flowers, one healthy and the other weak, that doesn't mean that only the weak one needs you to water her and the healthy one doesn't need water, no, both of them need water even if one needs more than the other, they both need it, this is the obvious fact that the mother completely missed, which caused the healthy flower to wither too.
The psycho, even though she is not guilty of having become a psycho because this is a result of having grown up in a dysfunctionnal environment, is still responsible of her actions and she acknowledges it when she states that she makes her own choices. Indeed, if there is a choice, that means there are several options to choose from. Meaning that she could have choosed another way to deal with her issues. By stating herself that she makes her own choices, she acknowledges that she knows that there are more than one way to deal with her issues but she chooses this one. I feel sorry for her for having grown up in such a dystopian environment but I also acknowledge her responsibility for her actions so she is guilty, not me and not you.
Do you understand now?