How could I write a fake obituary for Hero in Much Ado About Nothing?
Because I don't want to leave this now unanswered, I'll assume you are asking 'Was there a fake obituary for Hero?'.
An obituary to be held was suggested by Friar Francis in Act 4 Scene 1;
And maintain that she (Hero) is dead indeed.
This plan did ultimately work, as its goal was to make Claudio feel guilty for his actions, and it did. In the end, Hero did properly marry Claudio in Act 5 Scene 5, proving why Much Ado About Nothing is a classic Shakespearean comedy.