It should be a simple matter of your friend adding you to their family and friends list (not HHA) in their account and then using the avios to buy your ticket. I have used my avios this year to buy tickets for friends in NZ and Oz. It may be, however, as mentioned above, that if your friend just joined BAEC and the only activity was transferring avios from QR and then trying to buy you a ticket, that alarm bells might ring. Unfortunately, if that is the case, phone call may be the only option.