Why did Elizabeth leave Washington square park? Would you make the same decision? Explain your response

In chapter twenty-nine, Elizabeth watches the appointed meeting spot from her hotel room. She has two tickets out of the country - one for herself in the alias Lisa Sherman and the second for David. Tyrese drops David off near the park where he's watched by Eric Wu. Elizabeth watches David's arrival but also sees that he's being watched and knows that she's going to have to simply leave again without talking to David. She goes out and gets a taxi to the airport.