I've only miscarried once, at 14 weeks, and I did not have a d&c. My doctor allowed me to choose whether or not to have the procedure after an ultrasound confirmed that my baby had died. He gave me 5 days to miscarry on my own, then scheduled the d&c for the 6th day because there was some sort of danger to my health. I miscarried on day 4. After my miscarriage they did another ultrasound to check for any tissue that was left behind. Did your friend have an ultrasound at her hospital visits? My doctor also manipulated my pelvis with his hands to feel for retained tissue. I'm not going to go into gory details, but at 14 weeks my miscarriage was nothing like a period, it was clear that my body was eliminating all evidence of the pregnancy.
Out of curiosity, is it possible that she is refusing a d&c and not telling you this? I refused a d&c, which is why my ob allowed me to wait to see if I miscarried on my own. I mentally couldn't handle the thought of a d&c, it felt too much like I was aborting, I felt that I needed to let God and nature take the lead in that situation. I know that it was the right choice for me. Possibly your friend feels the same and is hesitant to allow a d&c? They won't do one against her consent, unless she is dying.