Hattie,
I think you should keep the word "princess" in your translation. The cut is not just "slim".... ; and "princess" is not used only on diamonds.
Here is a couple of references:
http://www.thefreedictionary.com/princesse
http://www.m-w.com/cgi-bin/dictionary

I think this is how it's generally known

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Note added at 8 hrs (2007-01-28 10:11:01 GMT)
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White Short Sleeve Nurse's A-Line Uniform Dress by Peaches ...Product Details: Short sleeves A-Line with front & back princess tailoring Elastic back with small back belt 65%... Found at 1 store ...

French term (edited): découpe princesse

or princess cut

Encyclopedia Britannica and Vogue actually use the term princess style. Princess cut is used but not nearly as often and I think princess style sounds more elegant.

princess style-- A basic dress style using continuous vertical panels to shape the body without a waistline seam.
http://www.aleya.com/referencedesk/glossary.html

Encyclpeadia Britannica
Princess Style--in dress design, style of women's clothing characterized by garments that are closely fitted to the waistline, which is unbroken by a seam. The princess style first was introduced in 1848 but was little worn until the 1860s.
At that time, the princess gown was made of fitted sections of material, worn over a crinoline and flared out at the hem. The princess style continued to be worn…
http://www.britannica.com/eb/article-9061413/princess-style

60s PRINCESS STYLE DRESS VOGUE PATTERN B34 UNCUT
Pattern by: Vogue Pattern Number #1545 Copyright : 1960s The pattern is :uncut ... More Categories " 60s PRINCESS STYLE DRESS VOGUE PATTERN B34 UNCUT. View ...
www.goantiques.com/detail,60s-princess-style,1217084.html

• BRIDALGUIDE - Fashion & Beauty
... Pool says he is inspired by "glamour girls" such as Marilyn Monroe who flaunted ... Luxurious, glittering, princess-style gowns are among Pool's signature looks. ...
bridalguide.com/default.cfm?fuseaction=request&item_id=1438&page_num=4 - 32k - Cached - More from this site

• Manhattan Bride Wedding Magazine
Manhattan Bride Magazine is the place to find out ... Glamour ... If you've chosen a feminine, princess-style gown, consider subtle makeup and simple hair. ...
www.manhattanbride.com/beautystories/beauty6.html -

The princess cut is the most dramatic variation of the A-line dress. This style emphasizes the clean lines of the A-line by utilizing vertical panels that run from the neckline to the hem. The princess style provides elongating lines that create a slimming effect since your eye focuses on the length created by these long, smooth seems.[sic]
http://www.weddingsolutions.com/fashion_and_beauty/Dress_Sty...

Miniature Flower Princess Cut Dress 3 layered spaghetti strap dress. Skirt's outmost layer is English Net over Polyester. Bodice overlap is beaded with miniature flowers over satin.
http://www.cybernetplaza.com/page.asp?style=13448

Princess cut takes a lot of time so this suit is a definite keeper. Nice slim cut, no buttons, without the princess pieces. I love the light weight of Italian wool.
There was a cute Chanel jacket on ebay recently with this fabric. It was a below the waist, opened jacket with a convertible collar. I'm looking for a pattern like it.
http://sewing.patternreview.com/cgi-bin/review/readreview.pl...

Irish doll clothes for 18-inch dolls are sewn easily.
Sewing Pattern Book "Sew the International Wardrobe for 18-inch Dolls" - $21.95 ... costume was based on a simple princess cut dress with a gored or pleated skirt ...
www.infinitefreedom.com/internat-pages/irish.html