She should not need one if it is an in-transit flight online. Check the site
http://www.delta.com/planning_reservations...ation/index.jsp------------------------------
FRANCE (FR)
Visa not required provided:
- continuing by same or connecting aircraft to a third country
without leaving the airport transit area; and
- arriving and departing from/to a non-Schengen country
(see: TIRGL/SCHS ).
If transiting to:
1. Another Schengen state (as a ticketed point):
Schengen transit visa -issued prior to arrival- required,
unless holding valid Schengen visa for one of the other
Schengen states.
For details on Schengen Agreement see: For details, click here ;
2. Basle/Geneva (Switzerland): see "Warning" below.