My wife shot a 642 and a SP101 back to back two days ago.
The SP101 was a "OH, we're already done with 40rds" experience.
The 642 was a "do I have to pull the trigger on that 5th little bastard" experience.
9 ounces, cushy grips and a sweet single action trigger seemingly made all the difference.
I already knew that about her, but we don't own revolvers for some stupid reason (me selling them probably has something to do with that..haha) so I had forgotten what a shootist she becomes, and how giddy she feels plucking those spend shells out out of the cylinder when she's done with set of cartridges.
So, my point? Definitely let her decide on what is comfortable and dare-say-it FUN for her to shoot. If it's fun, you're gonna have to watch your a$$, cuz she's going to know to shoot the crap out of that thing.