ami wasn't the cause of it she was simply stuck in the middle of it. the director would still be obsessed with his first love and Taeyoung would still be traumatized even if they'd never met her.
if anything i feel bad for her since she had no good options in life to take; you saw how badly things went when she left but if she stayed then Taeyoung would've never gotten out of his depression, if anything he was showing signs of early abuse with the ways he treated her so it was likely things would become worse with her there to enable his escapism- no matter what she did she was never going to escape.
I really f*cking hate ami, I get it, she’s a naive indecisive girl. But she literally caused everyone unhappiness. Everyone was a little problematic, but ami was the cause of it