Ambi Sitham told the court that she sat next to Rebekah Brooks at the meal in 2003 and that Brooks had suggested they keep in touch.
She told the jury she went to give her telephone number to Brooks.
"Piers [Morgan] turned to me and said 'Careful - she'll tap your phone'," she told the court.
Cross-examined by Clare Sibson, representing Brooks, Ms Sitham told the court she was "definitely a little bit concerned" by Mr Morgan's comment.
"I wasn't sure how serious the threat was," she added.
Brooks denies all the charges against her and the trial continues.
More top news
As world leaders discuss emissions targets in Paris politicians in the UK want Heathrow to demonstrate it can meet pollution limits.
Under the new rule adults over the age of 18 automatically become donors after their death, unless they opt out beforehand.
Doctors have recommend Peter Sutcliffe be moved to high security prison, but the final decision will be taken by the justice secretary.