Justice is investigating former Secretary of State Hillary Clinton over the Benghazi issue and her emails, and some suggest for Lynch to meet with the spouse of someone under investigation is inappropriate.
Donald Trump was among those critics, calling the meeting "just something that you don't do from an ethical standpoint. It's something that is unheard of."
Lynch said the meeting with Bill Clinton was unplanned and said they talked about their families and did not address the Benghazi or email issues. She had just arrived in Phoenix and the former president was waiting to depart when he walked over to her plane to chat.
"Our conversation was a great deal about his grandchildren," Lynch said. "It was primarily social and about our travels."
Lynch was in Playa Vista on Thursday to attend a Facebook town hall forum on community policing.
Lynch is currently on a nationwide tour to highlight the role social media plays in law enforcement, both in helping to fight crime as well as build relations with the community.
The town hall meeting was streamed live on Facebook to millions of people.