Me, myself, personally, I really like a Sig P239 and the 9mm is pleasant to shoot, though I carry 357 or .40. Tupperware guns sure are light. My duty gun is a Glock 22 and, well, it's okay.
In general yes, but probably not necessary for someone who can handle a 12 gauge and is used to shooting, presumably, center fire rifles. The rifle shooting will have gained her proper trigger technique, and the shotgun will have inured her to the bang and the shove.