Not bad at all
I've gotten to shoot maybe 20 rounds of .357 Mag through my four inch GP 100 and it was actually kind of pleasent. Noisey as heck, more muzzle flip, but the recoil wasn't to bad.
It just felt like landing a really good right cross on focus mitts. Straight, powerful, the shock going through all the right parts of my body: My arm straight to my shoulder, through my core, and out the back leg, just like a right cross!
Of course I had a teacher with me that day drilling me on stance, and that helped a ton! Also the weapon has such a NICE heft to it! It just soaks up the recoil.
Let her try a round or two in single action with no added stress from you on her. Let her know it hits harder and is a little louder, but just keep her grip and her stance nice and tight.
For the record I'm pretty small. 5'6" and 140-150lbs, also I'm a n00b so take this with a grain of salt. I'm just happy to be able to answer a question instead of asking one!