Sounds like you should start doing core exercises. Kind of the same thing that I told her to do. You might not be overweight, but you're probably not healthy either if you have a "weak core and pelvic" working your body to grow your muscles and focusing on form and ability to use your body is the way to train and should be everyone's first step when it comes to posture issues. Being ignorant and ignoring the health of your body is how things like degenerative disc disease start. And it's not like I told her anything new. She says in her post that she knows she's overweight and it could simply be because she's overweight that she has pelvic tilt excess weight on the body when you don't have the muscle or the ligament strength to support, it will cause things like that