Originally Posted by flarmip

All BA LHR-BCN flights tomorrow are indeed fully booked - no doubt because all of the customers who could be reaccomodated from the 3(!) cancellations are already rebooked.

Still plenty of seats left to BCN on Vueling, albeit that would require a transfer from LHR to LGW.

Alternatively your wife should ask to be re-routed via alternative cities. I can't immediately see any Oneworld-only options with less than 2 changes or avoiding transfers between airports. But if you open it up to all carriers (bearing in mind BA must re-route "at the earliest opportunity") then you have 1-change options via ZRH, FRA, MUC, AMS, LIS or indeed the AC direct flight. Availability this close to departure does depend on class of travel though.

She should only accept a refund if she no longer wants to travel at all.