According to Hmong traditions, you can't date or marry her. Sure, her biological father was a Yang, but she's also part of Lee too since she grew up in Lee family and eat with them. If she has Lee siblings, then it's a no-no for sure. You're like her half-brother. I am in the same boat too. I'm a Lao and eat and grew up with my Lao family. My parents got divorced and my mom remarried a Xiong guy. I have Xiong half siblings. In my case, I cannot marry a Lao or a Xiong.