JMS wrote "Live From Al Capone's Tomb" so I guess it was his idea to have Janine run up & hug Egon with Louis Tully standing there as a way of saying shove it to the GBII Janine & Louis pair-off.
The episode is also a 1989 one, with Janine's (ugly) bob haircut.
I really like the NOW Comic's moment between Janine & Egon where they argue about it after he found out. James Van Hise had them confront each other about it, argue, make up & move on. It was immensly satisfying!
Thank Heavens they ignored it in the cartoon after "Elementary, My Dear Winston."