"Remember, I did win by more than 3 million votes than my opponent. So, it's like ... really?" Clinton said at the Women for Women International Luncheon in New York.
When CNN's Christiane Amanpour said, "I feel a tweet coming," Clinton shrugged, "Well, fine."
"If he wants to tweet about me, I'm happy to be the diversion because we've got lots of other things to worry about. He should worry less about the election and my winning the popular vote than doing some other things that would be important for the country," she said.
Clinton also said she was "on the way to winning," but lost after FBI Director Jim Comey's letter to Congress and WikiLeaks "raised doubts" and "scared off" voters.
Yet, when Amanpour asked whether Clinton takes personal responsibility for the loss, the former secretary of State replied, "Of course!" Clinton added: "I take absolute personal responsibility. I was the candidate."
In November, Trump beat Clinton in recently blue Wisconsin, surprising pollsters. Trump's frequent appeals to working-class voters and focus on manufacturing also helped to fuel close wins in Michigan and Pennsylvania, Democratic strongholds in presidential elections for more than 20 years.
The former Democratic nominee admitted that her campaign made mistakes, but she also said her team also "overcame a barrage of negativity, of false equivalency."
"I'm now back to being an activist citizen and part of the resistance," Clinton said, as the crowd responded with applause.
— CNBC's Jacob Pramuk contributed to this report.
Watch: Hillary Clinton claims the future is female
CORRECTION: John Podesta served as Hillary Clinton's campaign chairman. His title was misstated in an earlier version of this article.