But she did her best to appear carefree as she sashayed on to the stage to Abba hit Dancing Queen and joked about the coughing fit and collapsing stage backdrop which marred her calamitous conference speech in Manchester previous year.
But Johnson's recent comments about her Brexit plan, calling it "deranged" and saying it strapped a suicide vest to the British constitution, have angered many fellow MPs.
Britain "isn't afraid" to leave the European Union with no deal, she said, adding that "resilience and ingenuity" of people will see Britain through.
"I write this with heavy heart; however, we now need a proper leadership".
Speaking before her speech, she told Sky News: We do have the big ideas. Quoting the late Remainer Labour MP Jo Cox, May said we - as in the United Kingdom, rather than Cox's initial reference to the European Union - have "more in common than that which divides us". That "If we stick together and hold our nerve I know we can get a deal that delivers for Britain"?
She launched a ferocious assault on Jeremy Corbyn's Labour, describing the takeover of the party by the left as "a national tragedy" and his policies of nationalisation and shares for workers as "bogus solutions that would makes things worse".
'I was a party leader myself for 15 years and I know what the rules of party politics are, but now that the Tory party conference is over we should get down to business, ' Tusk declared.
Johnson, the figurehead for the campaign to leave the European Union and the bookmakers' favourite to replace May, has become the loudest critic, warning Conservatives that if they supported Chequers they could be signing up to the party's electoral death.
Air Force awards $9 billion contract to Boeing for new training jets
Two prototypes of the T-X were produced by Boeing and Saab , with Saab building components for the aft fuselage and other systems. The Air Force says this structure helped it trim the total cost of the program down from the original estimate of $19.7 billion.
Her speech was aimed at providing an upbeat vision for Britain post-Brexit - and after eight years of austerity.
One leave-backing cabinet minister told the Guardian that May was a "vehicle for Brexit", and she was likely to step down shortly afterwards; another suggested the optimal time to replace her would be in 2021, a year before the next general election is due.
Here are the main announcements from the Prime Minister following her speech on Wednesday.
The Conservatives' annual gathering saw civil war erupt within the party, while the Prime Minister tried to put on a courageous face and keep a semblance of unity. "Her strategy is to make pleasing noises yet say very little of substance, keeping the country in a holding position until her final betrayal is unveiled at the eleventh hour". "There are instances where I will see a Conservative colleague on the television saying they have written a letter to me when they haven't".
It was inevitable comparisons would be made with the man who has become her political nemesis, Boris Johnson.
May appeared intent on stealing Johnson's spotlight, scheduling a flurry of morning interviews at which she unveiled a new immigration policy a day ahead of schedule.
With no agreement with the bloc over the divorce or a future relationship, the last day of the conference marks the beginning of what some officials predict will be a frenzied couple of weeks of diplomacy between London and Brussels as the two sides try to secure a deal to end more than 40 years of partnership. She announced local councils would be free to borrow as much as they wanted too for a massive social house building program.
He stated: "It's absolutely ludicrous, there's never been a hard border in Ireland".
"So this is our proposal". We are both reflecting what the British people want in Brexit.