This would appear to be a browser problem and not a BT problem.
You should check your browsers "saved passwords" list and seek out the BT one's. You will probably find that your wife's logon details are saved there.
Once selected you just need to delete it from the list. It will no longer offer it when you try to log on.
You should also check for your log on details and check that it has the correct details stored. If the are not correct just delete it.
Even if they are there and correct it might be worth deleting them and when you next log on and you enter the correct details and you should then be offered the option to save them again in your browsers saved password list.
