Crystal Harris I'm Getting Death Threats ... After Holly & Bridget's Comments!!!

The Playboy universe continues to generate controversy nearly 10 years after Hugh Hefner's passing ... because his widow Crystal Harris is firing back at 2 of Hef's former girlfriends, Holly Madison and Bridget Marquardt -- insisting their ongoing public criticism is fueling a wave of harassment against her.

Crystal tells TMZ ... the former 'Girls Next Door' stars have spent years building platforms painting her as the villain in the name of empowerment and accountability ... all while refusing to handle their issues privately. Instead, Crystal says, they’ve chosen to air grievances publicly.

Crystal tells us their commentary has led to her social media being flooded with gaslighting, hostile messages and even death threats ... adding that no disagreement justifies that level of mob behavior.

As we reported ... Crystal and her attorney, Gloria Allred, held a press conference earlier this month, alleging Hefner kept a sex diary full of thousands of nude images -- some possibly underage. Crystal claims the sex diary and photos are waiting to be scanned and digitized by the Hugh Hefner Foundation -- where Crystal was recently ousted from ... she says she was removed as the head when she expressed concerns about the diary content.

She is now fighting to keep that content under wraps ... and wants an investigation.

Holly Madison and Bridget Marquardt released an episode of their podcast "Girls Next Level" following the presser, where they questioned her motives and found the timing very fishy with her just being booted from the foundation.

Crystal insists she’s tried reaching out to Holly and Bridget behind the scenes to resolve tensions quietly, but says she’s been met only with more public jabs -- something she believes keeps the drama alive, profitable, and confusing ... adding the same people who claim to stand against their abuser will minimize the very dynamics they publicly condemn, depending on who it benefits.

Crystal's bottom line? If Holly and Bridget truly want accountability, she says her door has always been open -- just leave the online pile-ons out of it!