I'm mostly just confused

so she... Did kill her team? If she killed them and is known to be psychotic why TF was she allowed on this mission? She's met him before and then killed her team? Did he wipe her brain? Why did she have to kill them? She just floats and then dies? Wtf is going on

TLDR was promised cosmic horror and alien vampie type men and was given a good start and then a disappointment