Continuing on with fran's post... film speeds below 800 ISO will not be harmed by the xrays used at security. Most people use 200 speed or 400 speed film, as both are more or less all-purpose.
eta: Your friend (or anyone) can request hand-inspection of film so there's no risk of damage. Tell her to be polite, but firm if necessary - I've had TSA Agents tell me 800 speed film won't be damaged. I don't trust that.
Also tell your friend to be sure to WAIT for the hand inspection! I completely forgot the first time, until I was on the plane, that I'd left my film!