You say she has a stunning figure - so it's all so very easy...
Just Google "super model in jeans and T shirt".
Show her the pictures.
And the pictures of the men hanging around.
Case solved.
So just do what's always been done...
Denim skirt, grandad shirt. Any flat shoe.
Spay on jeans, white T-shirt, heels.
Black leggings, black polo, pumps (very Audrey).
Little black dress, the no make up look, hair scraped back. Court shoes.
For a dressy version see above but with hair, make up and small earings.
Deviate with a crop top for T-shirt, a red dress for black etc.,
Through Autumn/Winter she'll need a jacket or two so go to M&S, Mens department and get a Blue Harbour dark blue sports jacket (slightly too big) and then to Gap (spend the money...) and grab a classic denim jacket.
I spent 30 years in the fashion industry and trust me, you'll never see a fashion editor at a catwalk show in London, Paris or Milan who doesn't fit one of these simple stereotypes.
Less really is more.
Encourage her to dress this way and she'll always look good and feel that she looks good.
Simple clothes, have fun with hair and make up.
Google any celeb image from the last twenty years and the picture is jeans and a white T-shirt. There's a reason.