The "Wannabe" singer, who is mum to the comedian and actor's 13-year-old daughter Angel, has asked for Eddie's financial records, so she can assess what he pays her monthly to cover costs for their kid.
"Eddie and Melanie have both established careers in the entertainment industry," her lawyers write in the new documents. "Melanie is a singer, songwriter and television personality. Eddie is a legendary comedian and actor."
"Until recently, Melanie has been fortunate in her career to sustain a comfortable lifestyle for herself and Angel. Unfortunately, Melanie's income has dramatically reduced, such that she must consider modifying child support for the first time."
Mel B's representatives insist she made "numerous efforts to resolve this case without court intervention without any success," adding, "Melanie was left with no choice but to file this."
According to records, Murphy previously agreed to pay Mel $25,000 (£19,300)-a-month in child support, as well as Angel's health insurance and a contribution to her education.
In 2017, during her ugly divorce from Stephen Belafonte, her ex-husband revealed that due to the couple's "extravagant and affluent" lifestyle, Mel B had "wiped out all her Spice Girls money - approximately $50 million (£38.3 million), if not more."
Angel is one of Eddie's nine kids, who range in age from 22 months to 31.