Mostly moisture issues. Chafing has all but been solved with the right combination of saddle and shorts.
These are multisport races between 24 hours and 7 days that typically include running, hiking, MTB, road biking, kayaking, rafting, etc, and for the 20 hours of the day that they're not sleeping, they're typically in the same base kit + additional layers or gear depending upon the discipline.
Just read your blog and it brought back terrifying memories of being driven around Sri Lanka!
I've never done adventure racing but I hiked through corsica for 2weeks carrying all my equipment. I found pantyliners useful. They're small, light, absorbant and you can change them easily and regularly - meaning something clean and dry on a regular basis, which is bliss when you're uncomfortable in the middle of nowhere. Just a thought anyway.
I recommend she head to the kiddie aisle of the grocery store and find the strongest diaper cream they have, preferably one with zinc oxide. I found that it both heals existing rash and creates a barrier to prevent moisture from coming in. The only issue is that it tends to stick on clothes and can be tough to get out, even with multiple washes. But has saved my ass many a time.
Best stuff ever!!! I did a 3.5 day Adventure Race in Wyoming last July and this stuff was awesome. As soon as I start feeling "wear & tear" during the long races my inside voice always screamed "noooooo". (No whining during adventure races). This stuff not only prevents chafing and irritation, it can actually resolve any irritation that has already started. Also, I use wet wipes on races longer than 24 hours when I pee.