Harris, who was engaged to Hefner before splitting with him a week before their wedding, claimed that the Playboy founder lasted "two seconds" in bed.
Wilkinson told Life & Style: "I thought she'd be classy about things [following their split]. But it's not classy how she's opening her mouth the way she is.
"She should've kept her mouth shut, been a bigger person and just walked away. She looks like trash."
Harris said previously: "Then it was just over it. I was like, 'Ahhhh'. I was over it, I just, like, walked away. I'm not turned on by Hef, sorry. He doesn't really take off his clothes. I've never seen Hef naked."
Wilkinson, who has a 19-month-old son with NFL star husband Hank Baskett, insisted that Hefner should forget his relationship with the 25-year-old and move on.
She added: "Hef's been Hef for how many years now? He needs to move on and keep living his life!"