She is tougher than the local boars that roam the forest, but not by a significant amount. She has a slightly smaller pig "guard" (Porcine Entourage) who follows her around the farmyard and helps her in combat. She will not be hostile unless you attack her or her guard, or you happen to be one of Ma Stonefield's veggies.
She has to be killed for a quest because she grew fat and won competitions by eating from Ma Stonefield's veggie patch.
Princess used to be accompanied by two of the Porcine Entourages. However, sometime in early 2008 ,one of the guards was removed from the game making completion of her associated quest much easier to complete.