This is c&p-ed from an email from a friend, but here are some exercises to help support the joints as the ligaments continue to stretch and relax. Birth may not be an immediate solution; the hormones that make the ligaments relax can remain in your system for up to 3 months PP. a support brace can help tremendously, as well.
So Planks (probably on her knees to start unless she feels strong enough to hold on her toes She could also do an Incline plank so elbows on a bench or couch with legs straight out behind her). Side planks. Same variations if she needs. Quadriped (this is on all fours with opposite arm and leg reach out. You can just do the leg extension to start or if she's strong enough do both arm and leg. Hold for 10 sec. then switch. The last thing is with a tube or cable. Wrap the cable around a base so she can hold both handles. Stand side on to the base and step away until the cable has tension. Hold both handles to her chest and press both handles away out in front of chest. (keeping good posture, tucking her hips under and bracing her core) The tube should feel like its trying to pull her so the idea is to hold a strong stance so she is fighting rotation. she can hold static like a plank for a specific time or move hands in and out from chest to do reps.
All of the exercises have her hold a strong pelvic tilt so there is no arching in her back and make sure she is breathing fully so not holding her breath or "bracing" hard.
Re: Pelvic pain? Exercises to help.
There are some great ideas here:
https://mutusystem.com/exercise-for-symphysis-pubis-dysfunction-spd-or-pelvic-girdle-pain-pgp-i-pregnancy-how-exercise-can-help.html
The biggest thing is: if it hurts, don't do it. Quadiped hurts like a biotch for me and has for many weeks; I avoid it in yoga and just do the "gently lift my knee off the ground" version. I'm plenty strong enough, but the pelvis issues are aggravated by the motion. Is your friend a PT?
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