How much one pays for the Dining Plan makes no difference.
Counter Service meal coverage is for: An entree or combo, a beverage, and a dessert.
If there is a combo plate at Pizzafari that includes a side salad then yes, that is covered by one's CS credit.
If there are no combo plates, and each item must be ordered/paid a la carte, then no, the side salad is not covered by the CS credit. A Guest wishing to add this side to their meal can order and pay for it.
Some Guests may in the past, present, or future be given a side item at no extra charge. This is Pixie Dust at play, and is NOT the norm on the Disney Dining Plan.