Family arguments picking sides?

Whenever my parents fight, my sister tries to be a pseudo-psychiatrist and tries to be on both of the sides of the argument. Like when they fight, she will say to my mom something like "You shouldn't do this", which my dad uses for ammo against my mom, then my sister says something like that to my dad, which my mother uses. What she does doesn't help, and when it doesn't work, she starts crying and yelling "STOP YELLING" or something along those lines, which just pisses of my parents more cause they have to deal with a crying 13 year old. How can I teach her that she should either pick a damn side or stay out of it, cause shes making things exponentially worse. I'm not sure if this info is needed but I am 14 years of age.