I agree it's a kind of a no-brainer that save the date cards are only sent to those that you are definitely inviting - as obviously if you're not invited, there's no need to save the date, eh? 
But it sounds like the bride is much too far into bridezilla-land to understand at this point that she's committed a huge breach of wedding etiquette. Nor does it sound like she cares.
I quite frankly don't understand her desperate need to get Tiny to do this, to the point of alienating her. To be honest, I would be embarrassed to ask a guest at my wedding to do the decorating, much less someone that wasn't attending. Even asking guests to help kind of smacks of "hi, here's the invitation to the wedding, please bring streamers to hang and a table arrangement to share. " 
I was curious - did she have a hen do for this shindig?