Opinion without much experience is more likely.
It is fine to think that after reading my post, but I have owned or shot revolvers of varying size in multiple calibers (from .22 to .357). I'm not too sure what "qualifies" one to speak on self defense though, do I have to stop five different attackers with lethal force, in separate occasions before I have the experience?
The question initially asked was on gun suggestions (or opinions). If a J Frame works well for you, that is great... And I mean that with absolutely no sarcasm. If you want to suggest a revolver, go for it. In the end I'm sure the sister will find something to suit her needs.
I'm not arguing that revolvers are a very complex design requiring a bunch of thought to shoot. I'm sure most people here agree that operation is simple. Pull the trigger, it goes bang... But the same can be said for a Glock (or similar pistol). No manual safeties to worry about, reloads require less thought, greater magazine capacity, and a shorter/lighter trigger than something on a J Frame. The Glock trigger pro could be a con for some people though, and that is why choices are great.
You mention that SA is the preferred way to engage a threat (which I agree). If that is the case, why "handicap" yourself with long DA pulls when you could choose something else? Personally I doubt many of us would bother to switch to SA if our lives were in immediate danger. Another option for that perferred means of carry would be a DA/SA pistol. At least with those you have the benefit of SA after the first shot. Note that I truly do not advocate one form or the other, as I have changed a few times myself (SA 1911 to striker to DA/SA).