I'm not the type to burst bubbles, but I can pretty much guarantee the lady is Korean. That's just the way the market is in this town. She may be a nisei Korean-Japanese, sure, but ethnically Korean. I'd bet the farm on it.
As for the tip, once you are in 5-benji territory, there really aren't any set rules. You are in Wall Street territory. You do you. But for that price, I wouldn't have been surprised at BBJ at all.
Glad you had a nice time.