"Estimate the probability the nun passed some point on the path at the same time on both days"

Look, I read it the same way you did, and have arguments for the answer you believe to be correct. However, the question can be interpreted multiple ways. You and I read, "what's the probability she will be in at least one point on the path at the same time" others are reading, "what's the probability she will pass at any one particular place". And then one guy, who knows how he's reading it.