We actually don't, other than the U.S. government claiming she is. The timing of this seems quite odd considering the current government just lost an election, and has a history of blaming things on China.

> but we don't have any evidence of that?

Only accusations and suspicions at present, possible evidence in the future.

I don't have a deep understanding of the events, but my superficial impression is that China set up a shell company (Megaspeed) in Singapore, and put this woman in charge of it. She then persuaded Huang to engage in intercourse of the physical and commercial varieties. I get the impression he may have convinced some US officials to look the other way, to not dig into the affairs of the "Singaporean" company. That's where he may have strayed from "sucker" into "co-conspirator."