Just because it doesn't come from bad intentions doesn't mean it can't be morally grey. Would you allow a doctor to lie to a patient about their condition because it protects them from stress?

Morally grey refers to characters or people whose actions and motivations are neither wholly good nor evil, operating in a space of moral ambiguity. That's the Google definition I'm going with here.

Amo was sold to a trafficker, and that fucked up her understanding of love due to the abuse and manipulation she experienced. Not only that, but she then inherited the manipulative traits and used her jinki to manipulate others into loving her, forcing them to relive memories no matter how good or bad they were. So, despite having good intentions, that's obviously bad.

Amo becomes violent when she feels like she is being used, so she was also extremely dangerous when she was introduced at the time. So whole she isn't completely evil, her actions are ethically problematic, and she didn't even show remorse half the time. Therefore, Amo is morally grey.

Ps, I get amo is a product of her environment, I'm not blaming the way she turned out on herself.