Versailles is a toss up for a kid that age -- make sure she is really interested in doing it.
If the Notre Dame Tower is open definitely take her up to the gargoyles. My daughter loved this at 12 ; unfortunately the first prevented my granddaughter from enjoying it at 12. Watch the Disney hunchback movie before you go; the gargoyles play a major role.
Chateau Vincennes is right in town on the metro and a good old fashioned castle -- easy visit and perfect for kids. I got my grandson a cardboard castle kit in the gift shop and he was really thrilled putting it together.
Get Eiffel Tower tickets ahead of time so your line time is as short as possible. My granddaughter loved buyin a bag of ET shaped candy in the gift shop for her friends back home.
The Bouillons are cheap and a great place for kids to try out exotic foods without a big investment; my granddaughter tried snails at Bouillon Chartier Montparnasse. The menu is huge, mediocre (but fine) and has kid friendly as well as more challenging foods. The one on Blvd Montparnasse is also a stunningly beautiful room.
Walking along the right bank of the Seine there are places along the way for kids to climb on the wall or play -- and it is just a pleasant walk -- plenty of places to get drinks or treats and of course you can carry your own goodies.
when in Paris with kids we made a ritual of letting them choose a fancy pastry from a bakery every afternoon -- we would either take them to a park for a snack or take them back to the apartment to have after dinner. Kids love the choices and getting to choose -- it is a seriously cheap way to let them feel luxurious. If you have an apartment take the kid with you to the bakery in the morning to help choose baked goods for breakfast.