"I am here to stay," she told a Montreal radio station Tuesday.
"They will not wear me down. I'm a strong woman and have the resilience and, above all, I am a woman of conviction."
Disgruntled sovereigntists have sniped at Marois over her leadership for the last few months, criticizing her for not being aggressive enough in the pursuit of independence.
Three key PQ members — Louise Beaudoin, Pierre Curzi and Lisette Lapointe — quit the party in June, throwing it into turmoil that has seen it sink in public opinion polls behind Premier Jean Charest's governing Liberals.
More than 400 people gathered last weekend for the founding convention of a new citizens' group devoted to the promotion of sovereignty.
Many at the meeting of the Nouveau Mouvement pour le Quebec took shots at Marois.
"Yes, it's an attack," she told radio station 98.5 FM. However, she pointed out that when she returned to lead the PQ in 2007, it had 35 members in the legislature and deep financial problems.
Since then it has bounced back, somewhat, and is the province's official Opposition.
"I hope it will eventually level off," she said of the criticism, noting that the people challenging her share her goal of Quebec sovereignty.
She wouldn't speculate on whether the challenge to her leadership is being orchestrated by former PQ premier Jacques Parizeau and Lapointe, who is his wife.
"I've stopped trying to analyze that. I have so much work to do. I've decided to turn the page."
She is perplexed by the rise of a potential alternative party proposed by former PQ cabinet minister Francois Legault.
The right-leaning group, which hasn't declared itself as a party yet, is targeting social and economic issues and shelving sovereignty.
"Apart from the novelty, I don't know what he's proposing," said Marois, who insisted she has concrete plans for the province.
When it was suggested that Quebecers embraced the NDP on the same vague basis in the May 2 federal election, Marois said the situation was different.
She said Quebecers rallied behind that federal party because they knew it wouldn't take power.