To find the weight of Kristen's dog, you need to subtract 2.5 pounds from the weight of Milo's dog.
Milo's dog weighs 18.25 pounds.
Now, calculate Kristen's dog's weight:
\[ 18.25 , \text{pounds} - 2.5 , \text{pounds} = 15.75 , \text{pounds} \]
So, Kristen's dog weighs 15.75 pounds.