Answer:
Problem
Step-by-step explanation:
"Problem" is the most logical answer here.
There was not a "trick" in her route, there was not a "crease" in her route. The word "crease" is thrown in here to get you to think of it as an adjective in the same vein of wrinkle, as in creases or wrinkles in clothing.
Gap is the next most likely answer, however in this context it would not make sense. A traffic jam does not create gaps in routes, it halts them! Thus, the answer would be "problem".