Early on Tuesday, as the Congress ship seemed to be sinking under the BJP's huge lead, Ms Banerjee tweeted some words of advice for Rahul Gandhi's party.
Three hours later, the Congress announced its alliance with the Karnataka party, even opting to play second fiddle. The Congress and the JDS had been discussing a tie-up for the last two days, it was revealed.
Congratulations to the winners of the Karnataka elections. For those who lost, fight back. If Congress had gone into an alliance with the JD(S), the result would have been different. Very different- Mamata Banerjee (@MamataOfficial) May 15, 2018
Later in the afternoon, Ms Banerjee phoned HD Deve Gowda and congratulated the former prime minister and JDS chief for his party's performance and hoped it would form the government with Congress.
But no congratulations came from Ms Banerjee for the Congress whose vote percentage was higher than the BJP's. In fact, in a brief interaction with reporters on Tuesday evening, Ms Banerjee was asked if she had spoken to Sonia Gandhi too. She did not respond to the question, only turned around and walked away.
The last question she answered was, now that the Congress was ready to play second fiddle in Karnataka, did she expect it to do the same in 2019?
"You are asking controversial question. Let us hope for the better. I think regional parties are very strong and my language is enough for that," Ms Banerjee said.
A chill has crept into Ms Banerjee's ties with the Congress since Rahul Gandhi took charge of the party. In recent months, she has met with opposition leaders across the country to try to form an anti-BJP front.
That the front might be a non-Congress one emerged after Telangana Chief Minister K Chandrasekhar Rao flew down to Kolkata in March to discuss the option.
In her interaction today, Ms Banerjee said, "I am always saying, regional fronts and regional partners have a very important role to play. I feel both parties -- Congress and BJP -- must remember that and not treat them casually."
The centre, she said, is a policy maker, but states implement policies. "Whoever the national party is, you have to take into confidence the regional parties if you want to survive," Ms Banerjee said.