I dunno how much help martial arts would be in that situation. yes they would help.. but I would definately want a gun for back up. Plan is, use MA to knock them back then draw the gun.
In very close quarter combat(such as would likely be in a rape case where a gun wouldn't help) you are basically wrestling. Now in wrestling every lb matters. And who is heavier? The guy has a huge advantage there alone. I have seen skilled wrestlers fall to guys that are 40 or so lbs heavier then them that had little skill. And that 40lbs just happens to be near the average wieght diffrence between male and female in my area. So therefore martial arts likely wouldn't ensnare a victory by itself except in certian situations. A gun and melee weapon are good back ups.
Now if the female had some distance(used a wrestling/MA breakaway move and succede) then MA will come in handy. I say this because on average(in this area of course) women are quicker on their feet and more agile then men. And I have fought in those situations and brute force + weight doesn't help nearly as much as it does in very close quarters(wrestling type environ). However, if you got some distance a gun could quite possibly be better if you know how to use it. Not to mention it saves you from the iffy. That range is close enough that missing would be tough, and a gun wound will at least slow/weaken someone a bit. Thus giving you the advantage(hopefully).
Anyways these are just how I have seen it. The situation of a women with rape seems like a wrestling situation to me(and yes for those unaware wrestling is classed as a form of martial arts) and in wrestling wieght and raw muscle plays a big part(bigger the smaller you are... less as you get higher up). And the 40lb difference as well as the muscle power advantage between man and woman that I see here can easily devastate even someone with more experience. Thus, I see the breakaway and draw gun as a gals best chance. Best not to risk it. The more wieght added on the more likely it is to go in the guys favor, unless you break away.
As a last note I am assuming the assultant knows a bit about some fighting art. Reason being just about every guy in my area knows something about fighting.
Edit- IBCrayZ here is a link to a topic a couple months old on it. if you want to look through it that is. I know my stance hasn't really changed much(perhaps some specifics but not the overall thinking).
http://forums.eyesonff.com/showthread.php?t=65456
