They were the two most powerful women in Indian politics, and by no means, did they share a relationship beyond this precursor.
Let us rewind to the year 1999 Lok Sabha election -- when Congress leader Sonia Gandhi filed her nomination from two constituencies - Bellary, Karnataka, and the Gandhi family seat of Amethi in Uttar Pradesh.
The Bharatiya Janata Party (BJP) fielded Swaraj from Bellary -- the first-of-its-kind head-on battle with a renowned leader from a more-renowned party.
A lot of the credit for the propagation of the unsaid enmity between the two leaders goes to the BJP which projected Swaraj as the modern Indian woman as opposed to Sonia Gandhi's 'Italy-born invader' image.
Swaraj lost to Sonia Gandhi by a very small margin in Bellary.
Their rivalry reached an entire new level when, in 2004 -- when the United Progressive Alliance (UPA) had secured a majority in the Lok Sabha polls, Swaraj said she would shave her head and don a white saree -- a sign of mourning in Hinduism -- if Sonia Gandhi became the prime minister.
Sonia Gandhi, as history knows, did not become the prime minister, and Dr Manmohan Singh took the mantle forward.
In 2009, however, Sonia Gandhi called Swaraj a woman of substance, while delivering a Commonwealth lecture on women.
This was followed by Swaraj -- in 2014 -- praising Sonia Gandhi on the floor of the House as a graceful leader.
Cut to 2015, when in the eventful monsoon session of Parliament, the demand for Sushma Swaraj's resignation gained ground. Sonia and Rahul Gandhi had then brought up Swaraj's family's connection to Lalit Modi.
In August, 2015, a day after Sushma Swaraj explained her stand on the Lalit Modi controversy, there was no let up in the Congress attack on her with Sonia Gandhi rejecting her claims as "theatrics" while Rahul Gandhi said the whole matter was kept a secret as is done in a "theft".
People then did not take long to ask and ponder if Sonia had that controversial episode from 2004 in mind when she called Sushma an expert in theatrics.
Since then, the political animosity had only cooled down, upto a level where the two leaders had even begun exchanging pleasantries.
On late Tuesday night, when the unfortunate news of the untimely demise of Swaraj rippled across the social media, Sonia Gandhi's Congress were among the first ones to tweet.
"We are saddened to hear about the untimely demise of Smt Sushma Swaraj. Our condolences to her family and loved ones," the Congress said.
Sonia's son Rahul Gandhi also took to Twitter to express grief, and so did many of the Congress leaders.
Poll pundits and political watchers have long termed the political animosity between the two powerful women as mere that -- political. And perhaps, we will leave it at that.