Mel, 41, has filed for divorce from Stephen Belafonte and claimed in court papers that he had an affair with their nanny Lorraine Gilles.
The former Spice Girl also alleged that Belafonte got the blonde nanny pregnant and the pregnancy was terminated.
But Miss Gilles, 26, is said to be preparing a lawsuit against the singer, claiming she has lied about her in the divorce papers.
The lawsuit is said to be based on claims from Mel B that Belafonte and Miss Gilles had an affair which resulted in the pregnancy.
Mel B has also claimed that the nanny has access to sex tapes involving the couple which are held in a storage locker.
German-born Miss Gilles is reported to have submitted evidence which could disprove Mel’s claims.
Mel B alleges her estranged husband slept with the nanny during the seven years she looked after her three children.
She also claims that Belafonte forced her to pay for an abortion.
Her explosive allegations, detailed in court papers filed in Los Angeles earlier this month, state that Belafonte, 41, ordered Miss Gilles to abort the pregnancy and had paid her £240,000 for “nanny services”.
Film producer Belafonte denies the allegations. Mel, who married her second husband in 2007, claims he “went ballistic” after she sacked Miss Gilles.
Mel said she was devastated when Belafonte told her in 2014 that the nanny was pregnant.
She added: “[He] told me he wanted her to have the baby and all three of us live together. I was shocked and in disbelief.”
After Ms Gilles was fired in 2015, Mel said: “He screamed and yelled at me for three hours. He told me that Lorraine raised our children far better than I ever could.
“He then threatened, ‘You do realise that Lorraine could be a witness against you and give a story to the press and tell child services’.”
Mel filed for divorce last month citing irreconcilable differences and requesting joint custody of the couple’s daughter Madison, five.
Belafonte’s lawyers said: “Mr Belafonte is confident that the truth will come out when he has his day in court.”