You wouldn't get a new autobox for £1,400. All you would get would be a repair, or a reconditioned autobox. This is quite a simple 4-speed torque converter auto, same as used by Mazda in the Mazda 3 and not generally troublesome.

It's probably better for her now to get it to a member of www.fedauto.co.uk. They generally know their automatics far better than any Ford dealer. They'll fix it and find out if the Ford dealer had missed something fundamental (such as servo valve box seals) and give her a written report that she can use as the basis of a small claims track action against the dealer. Warn them first and if they don't capitulate, start the action using www.moneyclaim.gov.uk