Her lawyer, Pierre Cornut-Gentille, said in a statement that the interview had been taken out of context and that she had always done her utmost to remain discreet and not appear to have a public role.
French financial investigators are widening their probe to include two of the Fillons' children, who were also hired to help him out, a source told Reuters.
Fillon himself pressed on with campaigning in the Ardennes region in northern France, telling a rally of about 1,000 people to "help him resist" against orchestrated efforts by his political opponents to break him and the party.
He once again defended his actions as "nothing illegal" and sought to grab back the political high ground by attacking the other presidential candidates.
"I feel like someone who is being attacked unjustly on all sides. But I am ready to defend myself," he told reporters earlier in the day when a few cries of "Resign!" rang out from a crowd.
French lawmakers are allowed to employ family members, but the suggestion Penelope Fillon did no real work has damaged Fillon's image, and could yet put him in court.
Fillon has said the work was genuine and will not stand down unless put under formal investigation. He held an emergency meeting with party grandees on Wednesday in which he urged them to stick by him for another two weeks - the time he estimated a preliminary investigation would take to run its course.
But some appeared unwilling to give him that much time after one poll showed the hitherto favourite would be eliminated in the first round of the election on April 23.
Another survey showed 69 percent of people wanted Fillon to drop his bid.