If you search the BA "Your Questions" database, entry number 958 discusses refunds. Basically:
1. Passenger and government taxes are fully refundable...
2. Do it online - ringing BA will cost you £30
3. On a semi or fully restricted ticket, the refund will cost you £15 online
And finally:
"This refund fee will be collected from any monies due to be refunded back to the customer from their ticket, dependant on the fare regulations, including taxes, fees and charges.
However, if the refund amount due to the customer is less than the applicable refund administration charge then no refund will be due to the customer."
I suggest someone help her process the refund. You'll need to log into Manage My Booking and there will be a link somewhere for refunds