Mayor Aki-Sawyerr's problems have showcased some of the political tensions in this youthful democracy, which emerged in 2002 from a decade-long civil war, and where elections are due in June.
"My biggest shock has been to see programs, interventions, initiatives held back because of a perception that I am a political opponent as opposed to collaborator in development," Aki-Sawyerr, 55, told AFP from the newly-built skyscraper she works in -- a donation from the South Korean government.
A dual British national who trained as a chartered accountant and cut her teeth in London's private sector, Aki-Sawyerr returned to Sierra Leone in 2014 to help fight Ebola -- work for which she was awarded the Order of the British Empire.
She says she has no plans to leave Sierra Leone, although she has lived apart from her husband and now-adult children for eight years.
As mayor, Aki-Sawyerr has secured large sums of external funding, including a $1 million Bloomberg Philanthropies Award.
But domestically, she has raised hackles with her brisk style -- preferring her own, internationally-educated teams rather than veteran civil servants for major projects -- and plans to streamline outdated processes.
She has been audited, investigated for corruption and summoned to testify about her initiatives in parliament.
She is also fighting charges of obstructing the police and disorderly behavior over the arrest of one of her city councilors.
He is accused of incitement over cost-of-living protests last August that spiraled into anti-government riots.
It is common for Freetown mayors to go head-to-head with the central government.
But the backlash Aki-Sawyerr has received for doing so seems unprecedented.
"You need to know how to deliver, but you (also) have to play the politics," said activist Valnora Edwin.
"Unfortunately she seems to be falling directly in their trap -- she might have a court matter until it's time to nominate candidates for elections, and then she will not be suitable (to run)."
- Reforms -
One of Aki-Sawyerr's key goals has been to overhaul the city's manual taxation system.
"I kid you not, it was a book -- it was a ledger written in by hand," she said.
With financial support from the UK government, the mayor had satellite images taken and measured rooftops and other metrics to build up a digital property tax database.
She claims to have brought 70 percent more taxpayers into the system. She also raised rates on those already paying tax.
But within days of its rollout, the program was frozen by the national authorities for nearly a year, and compliance remains low.
One resident who refuses to pay his property tax is lawyer Chukwuemeka Taylor. He says it is unfair to raise rates on existing taxpayers, while providing inadequate services.
"I have to do the roads myself, I have to do the drains myself, and I'm paying property taxes?", he said, accusing her of milking the tax issue to appeal to poorer voters.
- 'She talks to you' -
The mayor does have sympathisers among lower-income residents.
"She has a lot of challenges... but she still is pushing," said Marie Bob-Kandeh, head of a market women's group.
Last year, the mayor provided shades in markets to protect vendors from the hot sun.
In the slums, she has worked with donors to construct public toilets and water taps.
"She talks to you," said Nancy Sesay, a resident of Susan's Bay slum. "When there is a problem, she comes."
Presidential, parliamentary and local elections are scheduled for June 24.
Aki-Sawyerr says she intends to run again for mayor. But her party is expected to tap her as running mate for the presidency against Bio, who will bid for second term.
Asked whether Sierra Leone is ready for a female vice president, Aki-Sawyerr said: "I think people respond to what they're presented with, and if they're presented with the right person, they respond to that."