Even without suite upgrades, she shouldn't take for granted two key things as a Plat: you almost always get a good room (top floor, view, corner etc...) and Plat 500pt bonus per stay gets you enough bonus points over 25 stays in a year for a free night at some pretty nice properties. Maybe our expectations are low?
We just did Sheraton Arabella Munich (suite), LM Nice (corner room with great view), LM Monaco (topfloor sea view, followed by really nice crystal suite), Sheraton Genoa (corner suite), Sheraton Roma Golf (junior suite), FP Bolzano (huge suite with view). Those were all points or cash/points stays and in most cases were not jaw dropping upgrades but we really enjoyed them. The two LMs comp'd us nice, local bottles of wine to enjoy on our balcony. So my wife is fully behind my SPG Plat status. To her the ability to stay somewhere way out of our usual price range like St. Regis Rome, Excelsior Florence or Westin Paris and not getting put in a closet because we are staying for free is reason enough for a few odd nights here or there.
You might try the Westin in Avon, Colorado where we've always gotten amazing 1 bedroom suites with kitchen and fireplace in the off season.
Good luck making the case!
P.S. We don't care much about lounges (of the list above only the Arabella Munich had a decent one but the Westin accross the road is much better if you like lounges).