Mia kept talking to herself in the mirror like an insane patient, she was holding a small dagger in her hand and was practicing on how to stab people with her reflection at the mirror.
In as much as she has been trying to control herself and keep pretending that she was still sticking according to Mr Lorenzo's plan this was the only thing she did to keep herself in control.
Practicing everyday on how she will stab Jadon with every single strength in her just like he did to her sister and also talking to herself was the only thing that helps her control her anger and manage to keep her going.
She was patiently waiting for the right time to come.
Hearing that Jason was dead was not enough for her yet, the only confirmation that she needed was seeing Jason's dead body with her own two eyes, that was the only thing that can ever convince her that Jason is dead.