Get new friends.
Now that that's out of the way, there may be no changing her mind. When people have their mind set as to whether or not to have a gun in the house you never REALLY change their mind 100%. I would suggest explaining to her that accidents can happen to you, her, or future children each and everytime you get into a car, but none of you are going to stop driving. I'll bet she eats fast food. Guess what? It causes obesity and heart disease, but I'll bet she doesn't worry about that.
Check this site for some facts.
http://www.guncite.com/gun_control_gcgvacci.html
Guns don't kill people, stupid people with guns kill people. If you're smart about them they are no more dangerous than anything else.