@Jips
Sakurako may be a bitch, but shes not scum.
Also Iori may have won the lottery, but all that money was basically used for this trip. And how would Sakurako even know that he won or even how much he has?
Its clear that Sakurako just genuinely likes him, she even tried to prevent him from going on the trip in the first place.
If I had to guess, she probably found out from someone that Iori and Chisa arent really dating, then rushed over to Okinawa to make her move before something really happens between Iori and Chisa.