She and her dog both have a serving before bed so they eat 1+1 = <<1+1=2>>2 servings a day
She wants to have enough for 30 days and they eat 2 servings a day so they need 30*2 = <<30*2=60>>60 servings
Each jar has 15 servings and she needs 60 servings so she will need 60/15 = <<60/15=4>>4 jars of peanut butter
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