156 more miles.
My Work:
The Sister drove 5/4 of 156 miles. The "of" stands for multiplication. 5/4 * 156/1
After we solve the equation, we learn that the Sister drove 195 miles, which would mean that the sister probably drove too far, leaving Nicole to drive back for them.
Because Nicole is driving the rest of the 195-156 miles, if we use the triangle sum method from elementary school, we can flip the answer to 195-156 with 156 and know that the Sister drove 156 more miles than Nicole without having to know how far Nicole drove.