The fact that they would rather have the people still doubt Ashtarte to be the darkness and think she killed her sister than to reveal that Amaryllis was a homunculus just so that she would be remembered fondly shows that her family is stil choosing the fake sister over the real one. Ashtarte is still alive and has to live with the people's judgement yet they care more about the memories people have of Amaryllis. They claim to love Ashtarte but they don't. Even if they feel guilty, ultimately, the one they still love the most is Amaryllis.
The fact that they would rather have the people still doubt Ashtarte to be the darkness and think she killed her sister than to reveal that Amaryllis was a homunculus just so that she would be remembered fondly shows that her family is stil choosing the fake sister over the real one. Ashtarte is still alive and has to live with the people's judgement yet they care more about the memories people have of Amaryllis. They claim to love Ashtarte but they don't. Even if they feel guilty, ultimately, the one they still love the most is Amaryllis.