Speaking for the first time about her loss, she said in a statement that the anti-apartheid icon's death on December 5 left her without her "best friend, beloved husband and guide."
The Mandela family last week performed a traditional cleansing ceremony to end the six-month mourning period at the family home in Qunu, the village where the statesman was buried on December 15, 2013.
"I have been deeply touched and comforted by the affection shown towards my family and I since Madiba's illness through to the present moment," Machel said in a statement, using Mandela's clan name by which he is affectionately known in his homeland.
Machel, an advocate for women and children rights said she would focus her energies on trying to fulfil Mandela's last wish and build a children's hospital.
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"Children were very dear to Madiba and his last wish was to build the Nelson Mandela Children's Hospital," she said.
"This is my dream too and I wish it can be realised in my life time."
The construction of the facility to be located in Johannesburg has been delayed by funding challenges.
Machel is a member of numerous organisations, including The Elders, a group founded by Mandela in 2007 of prominent leaders tackling global issues.