In her speech at the launch of a book 'India's Indira' in New Delhi, Sonia Gandhi said the then Prime Minister had no time for "snobbishness, ostentation, or pomposity, and was quick to detect hypocrisy and insincerity".
Sonia Gandhi's speech was read by her son and Congress Vice-President Rahul Gandhi.
The Congress President said she had good fortune of living with Indira Gandhi for 16 years.
"The brand of patriotism that I witnessed in Indira Gandhi was a noble and generous one that she imbibed from the notables of the freedom movement --from her beloved father (Jawaharlal Nehru) above all, and from Gandhi ji -- her dear Bapu.
"It was an all-inclusive, all-embracing nationalism rooted in a philosophy of compassion. This made her a proud Indian but also a citizen of the world," she said.
Sonia Gandhi, who was born in Italy and married Indira Gandhi's older son Rajiv Gandhi, said the late leader was a "remarkable person".
"The Indira Gandhi I knew was the nurturing mother-in-law, mother, and grandmother. What a remarkable person she was -- how kindly she welcomed me -- nervous and shy as I was -- into her home; how patiently she taught me to adapt to the new country and family."
Sonia Gandhi said Indira Gandhi understood her difficulties, drew her into her heart and opened her eyes to India's great history and culture.
Indira Gandhi, the Congress leader said, had grown up in the heat and turbulence of freedom struggle, knowing wealth, sacrifice, comfort, deprivation, and sorrow.
"Her mother's illness and untimely death and her struggle as a young girl with lonliness and loss made her deeply sensitive to the pain of others and protective of them.
"She was a friend and mentor to me, careful not to impose her will -- except in little things like making me drink milk and eat spinach, which I detested, while I was expecting my first child," Sonia Gandhi said.
The Congress President said the late Prime Minister was at home with many cultures and milieus, read widely, and had a multitude of interests outside politics.
"Not everybody knows that she kept in touch with writers, artists and activists," Sonia Gandhi said, adding that her love for nature made her an ecologist miles ahead of her time.
She said Indira Gandhi will command special attention in her birth centenary year and hoped that the "real" Indira Gandhi will be known to future generations, including the values that "she not only stood for, but also lived and died for".