kelliebellie wrote: "I'm hoping you are talking about when you were fifteen..."

You don't think that I'm going to say anything much different, do you?

In Paris, the Galleries Lafayette has a fashion show with mostly teen clothing on Fridays at 3pm. They don't have them every week, but you must sign up ahead of time. You can do this at their website. My girls who were 14 and 15 this past summer liked it.
Their favorite thing in Paris to do was to take the Fat Bike Tour. It is a great way to see Paris. I believe they will take you to Versaille to ride bikes as well. We didn't have the time to do that, but would have if we did.
They liked shopping around. Museums were not top on the list. They did the Eiffel tower and the Arc di Triomphe and toured Notre Dame.
We tried to get into the other church with the pretty windows, but they were closed at the time we were there.
I would ask for her input. Definitely spend some time in the city of Paris. It was a hit with my girls.

My step-daughters loved Pairs too (1 17, 1 14 at the time).

Their favorites:

Musee de Cluny

Musee d'Orsay

Pompidou

Shopping some discount teen stores (they heard about them from local kids they met at a music club)

An obscure film festival in the Latin quarter

A couple of fou fou dinners (one Jules Verne)

Buying watercolors on Montmartre

the chance to practice their French.

my son was 15 when we were in France, and he told me afterward that he was sorry he didn't get to meet any French kids, and hang out with them (he speaks no French, but kids manage). This is why I stress involving them in planning...

Great ideas! Thanks for them all!

Will ask her to do some research.....she is taking French.....I will probably remember a bit....from many many moons ago ...and am so glad someone mentioned Mont St. Michael....brought back memories of my visit there when I was 19...a warm, sunny Sunday afternoon...hmmmm ..... another story...another time!