The story is quite good at making believable complex characters, sure Glen is a jerkass, but we see how he arrived at his current mindset, and has also positive characteristics streamin from the same place and as such not in conflict with his bigger than life ego, and we can see why Cecilia 7th place is atracted to such presence, even if acknowledged as a bit against her better logical judgment. And as such it's not strange for her to have similar fascination with glamorous Alice, even as she accepts she went off a deep end, and had to be stopped, especially as the core of their motivations are similar. And though, I laugh at the girls treating Cecilia following her desires as a, hopefully more healthy, continuation/fulfilment of Alice's one (that might be my cynism talkin'), but still it is in character for them to focus on romanticism of the connections, as to help them emotionally close that chapter.
The overall premise is 'everyone is flawed', and due to circumates anybody can end up acting vilainous or heroic