As with most things in self defense guns we are talking trade offs. In wet pack the 22magnum does more damage even out of a 2inch barrel, in a 4 inch barrel the difference is substantial. From a purely ballistic point of view 22 magnum wins. Now the trade offs, 22magnum out of a 2 inch barrel is VERY loud. It is a lot more expensive than 22 long rifle. With any small bore handgun shot placement is critical. So, if you have a limited ammo budget, I think a well practiced with long rifle beats a little practiced with magnum.
I would not recommend a Taurus 941 for defense to anyone who doesn't have very good hand strength. Their double action trigger pulls are very stiff even after a trigger job. A Smith & Wesson would be a much better but more expensive choice. If, she continues to use the bobcat, try to come up with a plan to deal with a failure to extract as the lack of an extractor is this little guns biggest weakness in my opinion.
So, I guess to sum up, to me ballistically the 22magnum is definitely worth it, both it and the long rifle have almost non existent recoil, but the magnum is very loud. I can't tell you which is better for you, but hopefully what little information I have provided will help you to make the decision of what is best in your situation.