It's exactly because he IS invested in her route that she will die. She will die if you are not in her route. Much possible if you are actually in her route, you will protect her from Vinny and Buddy, maybe getting shot because of that.
But if you are not with her? She have no one dude, everyone that once liked her either was pushed away or distanced themselves (Tommy and Riona) the only one that remained despite everything, which is the light she found is the MC himself. Without him she is alone to bear the burden of her mistakes and she can't bear that burden, which is why I say she will end up 7 feet under without the MC.