But I'm a little confused as to how the episode actually showed that. I know that was the intention and it would have fitted with the concept of Mega Evolution very well but it really didn't come through. There were no flashbacks to any happy moments between the two, the only flashback concerned Nurse Joy literally insulting Audino in front of her instructor at her graduation because she wanted to be placed with a Wigglytuff instead and felt intimidated by Audio's superior skill and experience. For most of the screen time those two occupied they spent it fighting. The only time they weren't fighting was when professor Sycamore was analysing the stones and in that scene they weren't saying anything to each other. The only indications of any friendship between them was the child saying "They normally get along," and the fact Nurse Joy said she was looking for the Mega stone as a gift. While it's open to interpretation this suggested the relationship was professional for the most part at best and strained at worst. It's hard to see it as being "true friendship," and certainly nothing compared to say Korrina and Lucario or Alain and Charizard. Even at the end when Team Rocket attacked the centre, there was no moment of realisation that they'd been treating each other poorly, it seemed more like an amicable agreement to put their differences aside for the sake of their jobs than the actions of two people who genuinely care for each other. In my opinion the episode wanted to show that true friendship shines through the roughest of arguments but the poor characterisation and ease at which Nurse Joy and Audino mastered Mega Evolution failed to convey that message with any degree of clarity. This episode smacks of bad writing. The disappointing this is, that the plot was good or at least typical for an anime filler. The true friendship trope could have been successfully employed if Nurse Joy and Audino had been written as better characters.
On top of this, I also think it's worth nothing something I mention on a thread about another episode is the tendency of the writers to give important life messages to the main characters by having them witness a random COTD have the experience. They did this most appallingly in "Splitting Heirs" where Bonnie and Clemont learn about sibling hood by witnessing the dispute and reconciliation of two brothers and their Meowstic. If the writers are serious about showing that "true friendship shines through the roughest of arguments" why can't Ash and Pikachu have a fight and Pikachu runs away. That would be far more emotionally intense and compelling than having the experience lived through a character as flat as Nurse Joy (and would be a great springboard for Pikashipping - in fact that plots literally crying out for fan fiction). And if you think Ash and Pikachu are too close to ever fall out, what about Clemont and Luxray fall out (it's happened before), or Serena and Braxien (surprised it hasn't happened already to be honest), maybe Deddenne get's sick of being babied by Bonnie (of course if that happened Dedenne would loose it's life of eating, sleeping and pampering and have to go back to taking care of itself so that one seems unlikely but it could work). Have the actual main characters experience and learn things for themselves rather than use invented and one dimensional inserts as teachable moments.