Zhang told one of the U.S. Secret Service agents who protect the property she was there to use the pool and later told a second agent that she had been invited to a U.N. Chinese American Association event, though club officials determined no such event was scheduled.
Zhang has been charged with making false statements to a federal officer and entering or remaining in a restricted area, charges that carry up to a five-year sentence in federal prison if she is convicted.
Zhang, who was shackled during the hearing, did not speak other than to say "yes" in response to the judge's questions about whether she understood the proceedings.
Zhang's lawyer, Robert Adler, countered with a different, possibly exculpatory revelation - he said his client had paid businessman Charles Lee US$20,000 to get into Mar-a-Lago.
Zhang was taken off the premises and Ivanovich questioned her further.
"He knew it was something out of the ordinary", Ivanovich said. The agent then immediately shutdown the device to avoid further "corruption" of the computer.
The first thing you want to do when you pull a USB drive off someone allegedly lying their way into presidential hangout Mar-a-Lago is plug it in your computer. She was carrying two Chinese passports, which she showed as identification. Even 7-Eleven convenience stores have video cameras, the defense attorney pointed out. He pointed out that Zhang made no attempt to hide her electronic gear while entering Mar-a-Lago and agreed to be interviewed for nearly nine hours. The room where she was interviewed didn't have that capability.
The Secret Service appeared to rely on Mar-a-Lago staff to determine whether people should be admitted through the security perimeter into the club when the President was there, allowing for the issue of whether Zhang was related to a club member to arise, according to Ivanovich's testimony.
There is no indication she ever got close to the President, who was in south Florida that afternoon and golfing nearby.
As for the malware on the thumb drive seized on March 30, prosecutors told the court Monday that when an agent attempted to decode it, the malware began installing an unusual file on the agent's computer. "We don't deny someone for having so many cell phones".
The agent who questioned her, Samuel Ivanovich, has testified for about an hour about what happened that day.
The prosector also described what authorities found in Zhang's hotel room.
The FBI is still investigating whether she is a spy, CBS News reported.
Yujing Zhang, left, listens to a hearing, before U.S. Magistrate Judge William Matthewman in West Palm Beach, Florida.
This may well be the case - but it says something troubling about the state of our national security if someone who is not a sanctioned and trained spy, who made such elementary mistakes in the course of intelligence gathering, was nonetheless able to briefly infiltrate a facility that frequently plays host to the President of the United States.
The Miami Herald has previously reported that Lee sold travel packages to Chinese customers that included tickets to Mar-a-Lago events.