The variables won't be set up properly and there's a failsafe to remove her again if it isn't on. The switch can be enabled on the Highwind through a debug NPC (found near the Chocobo Stables) but I'm a bit concerned about this crash you and Rosario are experiencing.
I'll sort this out. Can you tell me the exact moment when the game breaks down? For instance, is it after the FMV, the boss fight, when the screen fades out on the scene, etc. That'll help me pinpoint the cause faster.
Also, are the two of you running the game through Steam or is it the 1998 'original' PC release?
Edit: I can't reproduce a crash on either version and this issue hasn't been reported until now. Have you both installed the flevel & scene hotfix patches?
Looking at it, it looks like I downloaded the patches but somehow forgot to install them
I'll do that and report back if the issue continues. Thank you so much for the quick response! This mod has got me evangelizing to my friends who complain about how easy the vanilla game is.
Edit: Nope, still getting the crash. I'm playing on the 1998 release, and it pops up after Cloud uses the Phoenix Down on Aeris and the screen fades to black-- I get a soft crash and have the choice of debug or close application.