Vickers Killing Janek

In watching then sheen when Shaw tells Janek there is wilklo be no home to back to Vickers has an intense interest in what is being said. Janek sort of grasps what is going on and gets the Ion engine warmed up. If Vickers is really in charge and wants to go home why didn't she take over command of the ship by physically restaining/killing Janek? BY incapacitaing Janek would Chance and Ravel stop the intended Juggernaut collision? Vickers has motivation, she has strength and she has opportunity though just a few seconds to make a movie changing decision. No she takes the escape pod route,, Now that I think of about it why not take off for earth when the Last Engineer stated his throwdown with the crew and confront Janek then.