That the UK is still 'bold' but 'dependable', 'outward looking' and a bastion of free trade. She has done that in private sessions with several leaders and a press conference with President Obama.
But very frank words from the United States, Japan and Donald Tusk, the President of the European Council, will steal plenty of the headlines instead.
Remember she was an advocate, albeit a pretty quiet one, of staying in the EU in the first place, with the economy one of her main concerns. So Downing Street says she hasn't been surprised by the warnings about the future.
And perhaps dealing with public expressions of sentiments that have been already expressed in private isn't really the problem.
Perhaps the real difficulty for the now not so new prime minister is that the biggest demands on her abroad are the same as those at home. Other countries want more details of her plans for Britain's life after the EU.
But with no consensus, or anything like the details of post-Brexit Britain from government, there isn't that much that she can really tell them. The political danger of such a relatively blank page is that others will fill the space.
Theresa May's intention at this summit was to reassure other countries that life after the EU might be tricky to work out, but in the end, all will be just fine.