Why is Acosta hated?

What she did on her first night by shooting is a complicated scenario because she was surrounded by supernatural creatures and no police academy prepares you for that. She saw people being killed by monsters so yeah she would start shooting and she did not know who was monster and who was human. She also did not know that there were people around so she accidentally killed someone. I don't think it's her fault still everyone gave her a hard time while they were being nice to people who were way worse than acosta. Even after several episodes showing her as a decent cop why are people still hating her?

EDIT: I have read all the comments and people only have surface level-superficial reasons to hate on her. I never said she is the best character but you people are just hating on her for the trend. Everything she is doing has been done by others but you don't hate them half as much. Yes she is kind of an assholes but this much hate is undeserved.