Ms Abedin, who is the estranged wife of Mr Weiner, has been at Ms Clinton's side for two decades and has been a close confidante since she entered the White House as a 19-year-old intern in 1996, assigned to the first lady.
She then served as Ms Clinton's deputy chief of staff from 2009 to 2013, and as vice chairwoman of her 2016 presidential campaign and has been by her side throughout her nearly two-year pursuit of the White House.
"I have one daughter. But if I had a second daughter, it would be Huma," Ms Clinton said at the time.
Ms Abedin, 40, actually met her future husband through the Clintons in the early 2000s. When the couple was married in 2010, former US president Bill Clinton officiated at the ceremony. She and Mr Weiner have one son together, Jordan Zain, born in 2011.
The political aide, who travels everywhere with the Democratic candidate, arranging her schedule, accommodation and transport, accompanied her boss in Des Moines, Iowa, on Friday as Ms Clinton gave a terse statement about the reopened FBI investigation. But she spent the weekend holed up in her New York apartment as speculation mounted that Ms Clinton might be forced to sack Ms Abedin, or distance herself in order to quell the storm.
The trusted aide hasn't spoken publicly about the newly found emails but has reportedly told colleagues she had no idea how they ended up on the computer.
"The possibility that this device contains any emails of hers is news to her," a source familiar with the investigation and civil litigation told CNN. "The device supposedly at issue now belonged to Anthony, not her."
Ms Abedin testified under oath several months ago that she had handed over all of her devices that could hold emails relevant to the investigation into Ms Clinton's private email server.
She also told lawyers that, like millions of internet users who don't manage their inboxes, she never deleted old emails on her devices, either at work or at home. "I didn't have a practice of managing my mailbox other than leaving what was in there sitting in there," Ms Abedin said. "They all stayed in whatever device I was using at the time or whatever desktop I was on at the time."
The Washington Postalso reports Ms Abedin was not a regular user of the computer, and when she agreed to turn over emails to the State Department for federal records purposes, her lawyers didn't search the device for materials.
In February 2013, Ms Abedin signed a document in which she promised to "turn over all classified or administratively controlled documents and materials" before she left her government job.
She could be facing up to five years in prison, if found to be lying, Daily Mail reports.
Meanwhile, FBI director James Comey has come under fire for not disclosing the new discovery weeks ago, raising questions about why the information was kept under wraps until just days before the election.
The timing of his letter drew criticism from Democrats and some Republicans who cast it as unprecedented and as potentially tipping the scales in the presidential race in favour of Mr Trump.
In a scathing letter to the FBI chief, Minority Leader Harry Reid of Nevada accused Mr Comey of double standards by investigating Ms Clinton's emails and not possible ties between the Republican candidate and the Russian government.
"Your actions in recent months have demonstrated a disturbing double standard for the treatment of sensitive information, with what appears to be a clear intent to aid one political party over another," Senator Reid said.
"I am writing to inform you that my office has determined that these actions may violate the Hatch Act, which bars FBI officials from using their official authority to influence an election. Through your partisan actions, you may have broken the law."
Energised by the news, the GOP presidential nominee has rallied his supporters, calling the latest developments worse than Watergate and arguing that his candidacy has the momentum in the final days of the race.
"We never thought we were going to say 'thank you' to Anthony Weiner," Mr Trump said in Nevada.
The FBI is now preparing to inspect roughly 650,000 emails on Mr Weiner's laptop that it believes to be potentially relevant to the separate Clinton email investigation. How they may be relevant - or whether they are significant at all - remains unknown.
It is unclear whether the FBI will complete its investigation of the newly discovered emails before Election Day on November 8.
