Honestly, I like this kind of outcome. Like...after the previous chapter, I was cynically prepared for her to be revealed as a manipulative psycho because...that seemed to be the pattern they were going with.
Knowing that not every other character is out to kill them means there's actually potential outcomes aside from "and then prez turns the tables and they got killed by their own trap" and other characters can actually be more than disposable horror teens, which is cool.
And I guess that and maybe showing off her horrifying backstory and how weird specters' powers can be was more the point than the specter that...couldn't really do much aside from recycle the previous monsters/use up future chapters' designs? So they didn't really need to do a big show of defeating it once it became clear it was powerless against the new girl.