Self-defense on the "ground" is probably the most uncomfortable thing to learn for most women.  There is no "personal space".  It's hard to move.  It's too much like a real sexual assault.  That, of course, is why it's so very important.

Paul Vunak once shared this illustration with me to demonstrate the fallacy of "style vs. style" thinking.  Imagine 3 experienced fighters.  

Fighter A is a professional heavyweight boxer.
Fighter B is a jujitsu wrestler.
Fighter C is a karate man.

In fight 1, It's karate vs. boxing.  The boxer is agile and fit, but when he closes the distance, the karate man snaps a kick to his groin.  The boxer, unfamiliar with the low kick and unable to block it, drops his hands in agony.  The karate man is able to kick him in the head and run away.  Winner= Karateka.