Do they already have their own MDE accounts? If so, be sure you connect to their profiles in MDE, don't create new profiles for them. Otherwise, MDE won't know that Joe Friend in your F&F list is the same person as Joe Friend in your best friend's MDE account and won't recognize your best friend's tickets or link the LLs you book to to your best friend's MDE account.
If they do not have their own MDE accounts, you can create a profile for them in your MDE account.