Does it stay that way for a long time, or does it just flash white and then go back to normal?
Depending on which service agreement she purchased, it may still be under warranty, in which case they are pretty good about replacing bad hardware. If you go to
their support web site
you have to register to login, but you put the service tag number in there (usually on a sticker on the back of the PC) for the computer and look up the warranty info. Then get on the phone with their customer support and they will walk you through any possible trouble shooting steps to help determine what is wrong. If it's a known problem with those monitors, they won't have you jump through too many hoops before they just send a new one (with a shipping label to return the old one in the same box).
Dee