First: if you can't afford it, DON'T buy it. Practice avoiding temptation by standing in front of the mirror and saying "I can't afford that; I can't afford that; I can't afford that".
However if you can afford it, you might try these things:
Muse aloud from time to time about the terrible crimes against women. It helps if you can find some articles in the paper and casually point them out to her. After that, occasionally mention a gun
for her for her self protection. Then sign her up for the NRA and get her a subscription to
Woman's Outlook. Believe me, she'll read The Armed Citizen page and it will give her a lot to think about. At that point, find somewhere, preferably out in the boonies, where she can shoot at a really big target pretty close up (no discouragement in the early stages). If you have a country friend with a wife or girlfriend who shoots, that would be a great help. If your wife is afraid of handguns, start with a .22 long rifle (NOTE: don't start with anything that kicks) and slowly work your way down in length and up in caliber. Finally, take her to a gun shop to look for a gun
for her. If it turns out that she's a pretty good shot, stress the fun aspect of shooting together -- and be prepared to buy a new gun for her every time you buy one for yourself.
good luck,
granny geek
Hope this doesn't post twice - if it does, forgive me.