Just an observation, you're a guy, so any opinion, suggestion, thought, idea, cognitive content, intention, sentiment, view, judgement or impression you have as to what is best for your fiance, will be wrong. You can't choose the pistol for her or the best way for her to carry it. Only she can do that.
The only way you're going to get the right setup for her, is to let her learn what her options are and have her do the choosing. Your fiance can get more assistance from another woman that carries and shoots, than you.
For your part, be supportive and answer her questions, without interjecting your own opinions. I took my wife to a gun show, so she could see, touch, hold and functionally operate (short of the bang) every firearm that interested her. (She came home with a 1980s model Colt Mustang, which is her favorite.) Another suggestion is, take your fiance to a range where you can rent pistols and let her try anything she wants.
The old saying, "when momma ain't happy, no one is happy" is very true.