There are various ways to take out enemies, many of which you are already familiar with through by the main The Last Of Us campaign. Of course Ellie is weaker than Joel and she cannot take on enemies straight on with fancy melee weapons. An interesting new way to deal with enemies is, when both regular human enemies as well as the infected are in the same area, to use bricks. Throw them at humans to make some sound and the infected will assault them. This may buy you enough time to sneak the hell away.