We do know from this story she can discourage a rapist.... 
@Cyber Liberty A "date rapist",maybe,but not a "sneak up on them and knock them out/choke them out" rapist.
There just ain't no such thing as a defense against a surprise attack,and we shouldn't be teaching women,or anyone else,that there is because they (women,especially) need to be aware at all times that they CAN be vulnerable.
I state this because I have heard too many damn-fool women brag about not being afraid of rapists/being attacked,because "I can take care of myself".
It's called "situational awareness",and we ALL need to utilize that when out and about,regardless of size,weight,or gender.
Ever seen a 6'6"+ 250+ lb college football player get knocked unconscious with one punch by a man that was MAYBE 5'6" tall and 175 lbs. I have,and it was a face to face thing after the football player got pushy and mouthy with the wrong man. The short guy literally had to jump up in the air to knock him out,but that IS what he did.
And to add insult to injury,he made the big guy lay on the ground after he regained consciousness and tolerate the little guy giving his army surplus fatigue jacket and boots away to anyone in the crowd standing around who wanted them. This happened outside of the main entrance of a VERY popular dance hall in a resort town on a Saturday night,and there was a large crowd standing around and watching.
I have a feeling he never tried THAT crap with a stranger again.
I also saw a good friend of mine who was a 3rd degree Shorin Ryu karate blackbelt instructor in a Japanese DoJo get knocked unconscious with one punch in a bar fight. The problem turned out to be he was "TOO FAST". He was coming up with the 3rd block when the guy punching him out finally "got there". He was so used to sparring with other black belts that he just couldn't move "slow enough" to defend himself against someone that slow. Yeah,if he had gone aggressive instead of defensive,he would have won without question,but he didn't really want to hurt that idiot,and paid the price.
We ALL had a lot of fun the next few days trying to get him to demonstrate that defensive move to us.
You NEVER know who you are facing until it is too late to do anything about it but hope for the best.
Also,NEVER get into a fight to defend yourself. When/if you DO get into a fight,fight to take the other guy out ASAP and using a "take no prisoners attitude".