Benedict has known Una Stubbs (Mrs. Hudson) his entire life because she is a close friend of his mother. So the affection Sherlock shows Mrs. H is completely real and completely Benedict's doing (Moffat didn't write it in the script initially).
Elphaba should just pull a Sherlock. Show up when Glinda's boyfriend is about to propose and be like, "Glinda. Short version: not dead." <<<I'D WATCH THE HECK OUT OF THAT SHOW <-- I'm laughing really hard why<<<< Totes Mcgotes!