She would not confirm yesterday she had officially swapped support away from Mr Hide, saying he made his own decision.
Mr Hide resigned as Act leader, endorsing former National Party leader Dr Brash to take his place.
Mr Hide made the announcement at a joint press conference with Dr Brash. Mr Hide backed Dr Brash's leadership and said Dr Brash had now joined the Act Party.
Ms Calvert told the Otago Daily Times she and Dr Brash shared a passion for similar parts of the Act message.
Those parts included the "one law for everyone" policy and the concern about government borrowing.
"I don't want us to be Greece or Portugal. I would be very concerned if my own household was borrowing $100 a week it could not afford. I am really grumpy about the Government borrowing it for me."
She was also unhappy about the idea of different laws for different people, calling it a "significant concern".
Speaking from Auckland, Ms Calvert noted the predominance of Maori, Polynesians and Asians in the central city and said it was not possible to make different laws for different ethic groups.
"We can't hide from that. We have to talk about it and I'm not frightened about doing that."
Asked if she had told Mr Hide or Dr Brash which of the two she supported before the leadership announcement, Ms Calvert said Mr Hide made his own decision.
A caucus meeting would be held on Saturday to decide the leadership, and a board meeting would be held after it to endorse its decision.
"Last weekend, I was standing behind my leader. This weekend, I will be standing behind my leader."
Dr Brash (70) last weekend announced he wanted to step into Mr Hide's role to prevent the party being wiped out in the November 26 general election.
Dr Brash met Sir Roger Douglas and Ms Calvert in Auckland to discuss his bid. He needed three of the party's five MPs to back him.
Mr Hide, who is the MP for Epsom, will remain in Parliament as an Act MP. He would like to retain his ministerial roles but says that is up to Prime Minister John Key. Mr Key earlier said it would be acceptable to him.
Mr Hide said he had assured Mr Key the confidence-and-supply agreement Act has with the Government is safe.
In a statement, Mr Hide said he was proud of Act's achievements.
"It was Act's success in Epsom in 2008 that ensured the change of government. If Act had not succeeded in Epsom, Helen Clark would still be prime minister."
What Act had achieved in Government so far was not sufficient to reverse New Zealand's relative decline or to return it to a society where Jack was as good as his master, no matter the colour of his skin, he said.
That could happen only if Act succeeded at this year's election in greater numbers and help strengthen the John Key-led National Government.
REACTIONS
• Labour leader Phil Goff: "A relationship involving Don Brash and John Banks ... will allow National to pursue all the policies it has wanted to pursue but has been afraid to admit to so far."
• Green Party co-leader Metiria Turei: "Don Brash ... in 2005 helped divide New Zealand with his Iwi/Kiwi Billboards ... He will be quite happy to leverage votes from these same divisive tactics."
• United Future leader Peter Dunne: "Don Brash is a rigid right-wing ideologue - give him influence and a hand on power and watch the New Zealand we know become a harsher, more brutal place."
• New Zealand First leader Winston Peters: "It's not a threat to New Zealand First because we don't represent the narrow interests of the very few, which is a specialty of people like Don Brash."
