When Cara drives to work, it takes her 30 minutes to drive 15 miles. On her days off, she likes to drive to her favorite donut shop. It takes Cara 6 minutes to drive to The Dreamy Donut Shop at the same rate.
How many miles away is The Dreamy Donut Shop?
miles
Since Cara drives 15 miles in 30 minutes, her rate is 15 miles / 30 minutes = <<15/30=0.5>>0.5 miles per minute.
Therefore, since it takes her 6 minutes to drive to The Dreamy Donut Shop at the same rate, the shop must be 0.5 miles/minute * 6 minutes = <<0.5*6=3>>3 miles away. Answer: \boxed{3}.