The first argument, that he had a gun and if she cut him he would have killed her, is bogus. Once under his control, she could be raped and murdered anyway. But if she slashes or stabs him a good one, it might not just save her life, but the lives of others he might rape and kill.
Knives are ubiquitous, even in rigid gun control tyrannies like New York. And nothing quite gets the attention of a thug like their seeing a lot of their own blood.
Optimally, the first gunman would have bled out, and other than some laundry bills, that would be the end of the story.
In pace requiescat, culus.
A ball point pen, properly aimed into the eye, will reach the brain if driven home with sufficient force to hurt your hand. The key is aim and don’t hold back ... put that pen where the brain can get the message. A book slammed edgewise into the front of the throat will stop the wind of all but the largest vermin. A set of keys ... well, you get the picture. Do something, don’t play the part the attacker has planned for you. If you allow the attacker to control you, you are dead anyway.