Cassie is an athletic person and tries to drink at least 12 cups of water a day to stay hydrated while being active. Her water bottle holds 16 ounces. There are 8 ounces of water in a cup. How many times does Cassie have to refill her water bottle a day to make sure she drinks 12 cups?
Please reason step by step, and put your final answer within \boxed{}.
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