Nora tricks Pyrrha into believing that Yang made a bet with Jaune that if he makes it past NNN that she and her teammates would let him fuck them in every way possible.
Which was a lie as she knew that Pyrrha just needed a push to let their Fearless Leader know how she felt, and making her believe something (totally believable since it was Yang) wild would happen if Jaune-Jaune managed to make it all the way through the month, drop a little hint about 'making him fail herself' and Bam! Project: Arkos Complete!
Could even have Yang actually had made that bet without anyone knowing.
