Hello, unless you speak russian/ukranian, I can't find any website that offers online purchasing.
Why don't you contact something like sony or hp sales and see if they can get a keyboard with russian letter set from their european warehouses?
Alternatively, your friend can go out to a local store and buy an external keyboard with the letter set on it.
Or she could get a layover (basically plastic bag with letters that you put on top of your keyboard)