An interim deal on Brexit in December 2017 appeared to give her new impetus, and the much-anticipated reshuffle was arranged.
A series of junior ministers were swept aside into Conservative HQ as "vice chairs", opening up space for fresh blood when the job moves are completed on Tuesday; and new-intake backbenchers, including the young MP for Mansfield Ben Bradley, were also given campaigning roles.
But the day began in a farcical fashion when her Conservative party announced a new chairperson on Twitter, only to delete the tweet and later name another lawmaker for the post.
Farage asked for the meeting after Barnier met with anti-Brexit British politicians past year, including Andrew Adonis, from the opposition Labour party, who had advised May on Brexit until he resigned from his post in December in protest at her appeasement of hard eurosceptics.
Meanwhile, the Financial Times, a British newspaper, reported on Monday, citing government sources, that the United Kingdom wanted to stay part of the European Medicines Agency after the body moves from London to Amsterdam.
The Times' front page called the reshuffle "shambolic" while The Daily Telegraph declared it the "night of the blunt stiletto". It was one of several low points in a turbulent year for the prime minister, who took over the helm of a divided government and country in July 2016 after the European Union referendum.
But May, who heads a minority government divided over Brexit, had only limited room for change. He emerged from Downing Street after a prolonged meeting with his job enhanced, taking on responsibility for reforming social care as well as overseeing the NHS.
Theresa May would no doubt have liked to have reshaped her cabinet more - but while she is propped up by the DUP and has a party still split over Brexit, this is as much tinkering as she feels she is able to carry out.
No 10 sources said Mrs May is "disappointed" but respects Ms Greening's decision to leave the Government.
Environment Secretary Michael Gove, International Development Secretary Penny Mordaunt and International Trade Secretary Liam Fox all remain in the same jobs.
According to the newspaper, the new minister is likely to be placed in the ministry for Brexit and will work in parallel with Minister Davis Davis.
The European Commission said it's surprised U.K. Brexit Secretary David Davis is questioning its contingency plans for failing to get a deal with Britain, adding that it was only following the government's lead. But the former justice secretary has not been given the title of first secretary of state, which marked Green out as Theresa May's effective deputy.
Her shuffle was complicated by the resignation of the United Kingdom's minister for Northern Ireland amid a long-running political crisis in Belfast.
Confirming he was leaving May's top team after nearly two years as party chairman, Patrick McLoughlin - who was blamed by many Tories for the party's poor showing in last year's snap election - told Sky News: "I've been in the Cabinet eight years".