I have a post natal client, perhaps past the point of post natal as her daughter is now 18 months, who has the classic protruding lower ribs. I have cued her to keep her ribs down and back during pelvic tilts which has now programmed into her 'muscle memory'. She mentioned to me that she knew pregnancy permanently opens the pelis and was wondering if this is the case with her rib cage. Have I falsely been cuing her out of how her body should be sitting post pregnancy. Any thoughts are appreciated.

It could be that her psoas is shearing her ribcage forward. You could try releasing her psoas and iliacus and see if that makes a difference. Has she been experiencing upper middle back discomfort? Does she lift her chest high when seeking "good posture"?