gelphie chip within my brain reactived so have this:
another thing wicked (the film) makes entirely clear is that glinda and elphaba's hearts' desire is each other. which is exactly why they cannot ever have it, despite being able to grant everyone else their wish.
glinda gets dorothy home. elphaba leaves with fiyero. the people of oz are free of elphaba. the only people who don't win are elphaba and glinda.
if your heart's desire is something that you had with you all along, but you just needed the journey to find out, then that's exactly what the relationship between glinda and elphaba is.
upon seeing this brochure with the note (what's more romantic than a handwritten note from your lover??? roommate) elphaba refuses to leave glinda behind and practically drags her onto the train with her!! she needs her beside her!!
in wicked for good we see the note again. admist all the madness of being a political enemy of the state, elphaba keeps this brochure. she opens it and immediately reminisces not of fiyero but of glinda and hersel, when they were happy. that's when she then decides to visit Glinda before the wedding, despite being actively hunted by everyone in Oz.
their heart's desire have always been each other which they realise at the end of the musical but it's utterly tragic because for their desires to work, everyone else's must fail.