Mel B reportedly believes Stephen Belafonte and Lorraine Gilles "crossed a line" by having sex without her.

Mel B and Stephen Belafonte

Mel B and Stephen Belafonte

The former Spice Girls singer is being sued for defamation by her former nanny and in her documents, the German model claimed she used to have threesomes with her former employers - who split last month amid allegations the producer had been abusive to the 'America's Got Talent' judge - over a seven-year period.

And insiders told TMZ that Mel doesn't dispute the fact they had a sexual relationship, but she is said to have felt their deal was broken several years ago when her spouse and Lorraine had sex without her.

In her legal documents, Lorraine also denied Mel's claims she had been pregnant with Stephen's baby, insisting the 'Mama' singer had helped her get an abortion after she conceived following a one-night stand.

However, the 41-year-old singer - who has daughters Phoenix, 18, and Angel, 10, from past relationships and five-year-old Madison with Stephen - is said to be still insisting Lorraine was carrying the producer's child.

The former nanny - who is suing for defamation, libel, invasion of privacy and intentional infliction of emotional distress - claims Mel has portrayed her as a "homewrecker, prostitute and extortionist" but "in actuality," the 'Wannabe' hitmaker "seduced" her as a "naive and curious 18-year-old foreign exchange student ... with alcohol, fame and casual sex."

Lorraine claimed Mel confided in her when she first came to the States from her native Germany and told her she and her spouse had an open relationship.

Shortly afterwards, the trio had a threesome and Lorraine claims she continued having sex with Mel for the next seven years.

She also insisted in her legal documents: "At no point did Gilles and Belafonte engage in any sexual acts without Brown's knowledge or participation and at no point did Gilles and Belafonte represent to Brown that Gilles was pregnant with Belafonte's child."

Though the former 'X Factor' judge has accused Lorraine and Stephen of trying to extort her with sex tapes, the nanny insists she doesn't have any of them and when they did have sex, Mel would film the encounters and/or "take part in the menage a trois herself."

Lorraine insists she "loved" Mel and "still deeply cares for her children, but has been forever hurt and betrayed by" the star due to her "false statements and public disclosure of private, sensitive information in her declaration."

Stephen's lawyers have previously described his ex-wife's claims as "outrageous and unfounded."