Diastasis Recti happens to all women who are pregnant. However, a majority of women only have a small separation and it is a non issue. I would suggest she also look into the the MuTu system. Much better ratings the The Tupler technique. She should consult a physical therapist, preferably one with a specialty in women's health issues/pelvic floor issues. MOST IMPORTANT-NO CRUNCHES, SIT UPS AT ALL!! This will make it worse. The therapist will teach her exercises, although boring, like diaphragmatic breathing, correct posture and heel slides to help heal. Once she closes the gap, she can move on to other, more complex exercises. Note, even performing an exercise such as the seated leg curl can put strain on her stomach and should be avoided. Although surgery is a costly option, most surgeons agree that the sutures could rupture and that should be considered. If she has DR coupled with a hernia, then most likely insurance would cover the cost.
I am not an expert in this arena, simply did a lot of research for personal reasons. I hope she has good luck. I am happy to share any other info I have come across if you have a question.