Nadia's friend arrived just as she was preparing to leave. What would be the best transformation?

The best transformation in this case is "on the point of leaving." This phrase effectively captures the immediacy and readiness implied in the original sentence, indicating that Nadia was very close to departing when her friend arrived.

Using "on the point of leaving" conveys a sense of being in a transitional moment, emphasizing that her preparations were nearly complete. This choice aligns well with the original context, maintaining the timing and intention of the action.

The other options, while they suggest various states of readiness, do not convey the same precise timing or context. "About to depart" could work as an alternative, but it lacks the nuance of being actively engaged in the preparation process at that specific moment. The phrase "in the process of leaving" suggests that she is already leaving, which changes the meaning. Lastly, "ready to go" implies a state of readiness, yet it does not highlight the immediacy that "on the point of leaving" does. Thus, the first choice is the most fitting transformation in this scenario.