The octogenarian Mugabe has led Zimbabwe since independence in 1980.
Frazer was responding to questions about whether some kind of power-sharing agreement could resolve the impasse.
“We think in this situation we have a clear victor,” she said. “Morgan Tsvangirai won and perhaps outright, at which point you don’t need a government of national unity. You have to accept the result.”
But she added: “There may need to be a political solution, a negotiated solution.”