40-year-old Koirala, the granddaughter of B P Koirala who was Nepal's first elected primed minister, said the country never had any dispute over the issue of religion.
"I don't understand why peaceful Hindu state Nepal was converted into a secular state," she said talking to mediapersons in the capital.
Nepal was converted into a secular state three years ago by the Parliament.
"Nepal never had any dispute over the issue of religion. There was no need to change the status of the Hindu state as there was no problem in it," she said.
Manisha, a strong supporter of monarchy, said she had great respect for the late Prime Minister G P Koirala, her grandfather's younger brother, though she had some political differences with him.
He possessed a strong personality and was a dedicated politician, she said, adding he did whatever he thought was right.
Replying to a question on who should be the successor of Koirala, the Nepali-Indian actress said it is not necessary that his successor should come from the Koirala family.
The party's next general convention will decide who will be the successor, Manisha said.
"There should be cooperation among the leaders of the party not competition, she pointed out.
When asked if she is in race for the party's leadership, the actress said she has no interest in politics at this moment.
"I want to serve the country from outside politics," she said, adding "I will work for the benefit of children and orphans in the country".
She said her grandfather B.P. Koirala was her ideal in politics.
When asked about the possibility of the revival of monarchy in the country, she avoided a direct answer, saying "I am too small a person to comment on that".
On her professional work, Manisha said she will work in Nepali film if she is offered a good script.
She warned that the failure to promulgate the new constitution by May 28 will be "disastrous" for the country.
"I wish the constitution will be drafted on time, she said, adding it will be disastrous if it is not completed on time.
When asked about her marriage, the Bollywood star said she has not yet decided on the matter.
However, she underlined that she would like to settle down in her homeland Nepal.