Oh, that's VERY interesting. And yes, I am very interested in any translations and informations, so please keep me informed.
I have seen only the English text dump of Pokemon Crystal and it has nothing which could match Chieko. So, it seems like the event wasn't preprogrammed and was patched into the game using Mobile Adapter. The text does have only one strange thing related to Azalea Town - between Slowpoke text and GS Ball text you can see a dialogue of a Pokemon nicknamed Wooster (WOOSTER: Gugyoo...). There is no other reference to this and I've got no idea what it could be. Maybe a Japanese dump would help us in demasking its identity. But chances are that it's something meaningless and completely unrelated to GS Ball.
I think there's only one possible way to find something more about Chieko and GS Ball mysteries: Media Coverage. I'm sure that those events were somewhat covered in CoroCoro, Famitsu or other magazine like that. The problem is that those magazines aren't valued at all, so Japanese people just throw them away. Digging them out is gonna be very, very hard.
Speaking about magazines, I think I may have something relevant to your interests (although you might've seen this) - the GS Ball artwork. I grabbed it long ago from Pokemon Zeo, which had (very shallow) information on some old CoroCoros and some partial scans (like this one, I didn't cut anything out, I downloaded it like this, AFAIR). This section on Zeo still exists but many of the images are down. This just confirms that magazines did cover the Mobile Adapter features and that if we dig old issues, we may learn something about Chieko's event (maybe even her artwork... meh, I doubt it).
You could also try tweeting Masuda, although he's giving shitty answers to people (though most ask shitty questions).