She’s the one with a foul mouth.

The Brooklyn sergeant accused of stuffing her dirty panties into an underling’s mouth called his penis small — and subjected him to a raunchy rant about her wild, dildo-centric sex life, according to a complaint.

Sgt. Ann Marie Guerra, 38, allegedly humiliated Detective Victor Falcon by telling him that a female love interest likely rejected him because he was lacking downstairs, according to a complaint filed with the NYPD Equal Employment Opportunity Office.

“Sgt. Guerra stated to me that if the girl didn’t call me back, it is because I had a little d–k,” he said in the complaint.

Guerra — who allegedly shoved her undies into the detective’s mouth after he griped about her leaving them scattered around a unisex bathroom at the stationhouse — also bombarded him with crude tales about her own sexual conquests, according to the complaint.

“Sgt. Guerra stated that she used a dildo on her husband during intercourse,” the complaint states.

“On another occasion [she said] that she was home alone masturbating and her husband came home and tried to join and she said, ‘WTF this isn’t an invitation.’”

Guerra, the second-in-command at the 72nd Precinct Detectives Squad in Sunset Park, allegedly flipped out and rubbed her panties on the detective’s face, then pushed them in his mouth on Oct. 7, according to the complaint, filed on Oct. 10.

It also notes Guerra discriminated against Falcon by denying him accommodation for his special-needs kid.

Fellow cops have also complained about the sergeant leaving her underwear on the unisex shower knob and outside her locker for all to see, police sources said.

Guerra, a married mom of two, has also irked officers by going on man-hating rants and spouting off about colleagues having “little d–ks” on Facebook, a police source said.

Additional reporting by Natalie O’Neill