12:02 PM PT -- We've now learned Gloria Allred will represent the woman who made claims Kelly sexually abused her at just 13 years old in Detroit ... police are looking into the accusations.

The victim tells us, "Listening to R. Kelly's denials about what he did to underage girls like me was very hurtful. He needs to tell the truth and he needs to stop playing the victim. He was the adult and I was the child. He has no right to take advantage of me when I was only a 13-year-old child."

R. Kelly's ex-wife claims his abusive ways didn't end when they got divorced ... she says he tried to control her by cutting her off from child support.

A rep for Drea Kelly tells TMZ ... the embattled singer knew EXACTLY where to hit Drea where it hurt her most after she spoke out in June 2018 -- on a show called "Sister Circle Live" -- and alleged he'd been physically and mentally abusive during their marriage.

We're told the singer -- who has 3 kids with Drea -- had sporadically been paying child support, but lo and behold ... the payments completely stopped after her interview aired on TV.

Drea's team says her career took a hard hit after she had her first kid -- Kelly wanted her to be a stay-at-home mom, set strict rules for her and insisted she only work for him. When the marriage hit rock bottom ... she was a single mother without a job.

That control didn't stop after they split -- Drea says Kelly's unwillingness to take care of his kids was a form of control because he knew damn well she needed his financial support.

She says sometimes he would pay in full, sometimes late and sometimes nothing at all. Bottom line ... she never knew how much, if any, money they'd have to live on.

As for Kelly dumping all his problems on Drea -- she says that's a load of crap.

Although he ranted to CBS that he can't make money because of her abuse allegations, Drea points out the #MuteRKelly movement started well over a year before she spoke out.