You can transfer Avios from a HH account to someone who isn't in it, using the links available on the BA.com website ... I did just this very thing only last week. The system will only allow you to move Avios 'allocated' to your name, and not the total amount that 'belong' to other members of the account.

The usual table of fees (as given) apply ...

https://www.britishairways.com/trave...s/public/en_gb