I would suggest one of the S&W J-frame .38 specials. A lot of experienced shooters don't like the recoil of a .357 magnum in a J-frame and never shoot it. I believe the 9mm revlovers all require the use of moon clips but this is not a big deal.
In the .38 special caliber, she should initially shoot 148 grain wadcutters. These are about as mild of a load as you'll get. At the same time, they are pretty decent defense rounds because the flat nose tears flesh and tissue. Against heavy clothing (e.g., leather coats), then lack of penetration becomes an issue. Then she will want to move into the +p loads. First start with the 148 gr. wadcutters, though, until she gets used to shooting a handgun.
Most people suggest getting a hammerless model or a model with a shrouded hammer to prevent snagging when it is drawn from something like a pocket or purse. I have a model with an exposed hammer because I carry in a holster and I like the option of cocking and firing single action.