To make the vinegarette: place 1/2 the pint of blueberries in the blender with the balsamic vinegar, olive oil, lemon juice, and garlic. Blend on high until pureed and add salt and pepper to taste. Set aside.
Toss together remaining blueberries, shallot, pistachios, blue cheese, and spinach. Toss in with the desired amount of dressing and serve. Store any remaining dressing in an airtight container in the fridge.