did some of you guys recommending dogs miss what the OP wrote?
dogs arent for everyone.
as for the .22lr thing:
there is no guarantee that 22LR will kill a person, much less someone pumped full of drugs and adrenaline. ive seen one pound prairie dogs and squirrels shot with .22LR survive long enough to run fifty yards, are you going to trust it to stop a 200lb human being?
as for the .410:
http://www.brassfetcher.com/12 gauge.html
you are essentially firing
a third (or less) as much lead at your assailant with a .410.
both barrels of a .410 coach gun as was recommended would pack less stopping power than a single 2 3/4" reduced recoil 12ga round (of which she would have 3-8 more in a pump or semi), and if they missed or failed to stop shed be in big trouble. yes a .410 coach gun is better than nothing, but its
far from ideal.
if the op already had one (.22 or .410), and due to budget constraints
had to use only what was available, then sure use it. but he is asking what he should specifically
go out and BUY - and as such a .22lr and .410 are really bad choices.