I think that problem is that his MIL would fire one practice round and walk away. I know that's how my wife is. Better to start small and work up.
Boghog, how will she be carrying it? She she can tolerate something heavier, you may consider a steel k frame or Ruger equivalent. I have a 2" Model 64 (38 special) which is delight to shoot compared to any j frame. In a purse, I don't think the weight difference will be that noticeable. (I'm not recommending purse carry, just acknowledging that's how many women prefer to carry).