PM Modi cabinet: Nirmala Sitharaman is India's first full time woman finance minister. (PTI photo)

Nirmala Sitharaman's promotion is seen as the big news as Prime Minister Narendra Modi's new government starts work. She took charge on Friday as India's new Finance Minister, which puts her in charge of perhaps the most challenging assignment for this government.

Ms Sitharaman was Defence Minister in the previous government, so it was on her watch that India carried out air strikes targeting terror training camps in Pakistan's Balakot. The Balakot strikes were a big rallying point for the BJP as it campaigned for reelection based on its tough stand against Pakistan and strong decision-making.

Nirmala Sitharaman is the only woman in the Big Four, or the top four ministries. In the previous cabinet of PM Modi, she had then Foreign Minister Sushma Swaraj for company.

"Honoured and humbled by the opportunity given to serve the nation under your leadership," the minister tweeted, tagging PM Modi. "As a karyakarta grateful to my party BJP," she posted.

Taking over the Finance Ministry from Arun Jaitley, who opted out of the government because of his poor health, Nirmala Sitharaman's main agenda will be to arrest a sagging economy. She will also need to find the money to fund PM Modi's campaign pledges without undermining the budget deficit target of 3.4% of GDP for the year through March 2020.

Among the economic pain points that she has to tackle are weak farm incomes, job crisis and falling sales of key consumer goods, including cars and motorbikes.

The 59-year-old started as BJP spokesperson and remains one of the party's - and the government's - top defenders. She defended the Rafale deal in parliament and on television as Rahul Gandhi and the Congress relentlessly accused the government of corruption and crony capitalism.

Nirmala Sitharaman has never contested an election and has been a Rajya Sabha member since 2014.

She worked as a research manager for audit firm PricewaterhouseCoopers LLP in London and has a Masters degree in economics from the Jawaharlal Nehru University or JNU.

Nirmala Sitharaman is India's first full time woman finance minister. Former prime minister Indira Gandhi held the portfolio too, but as additional charge.