I'd make the observation that she probably wasn't wearing her "I'm a Chinese spy" hat when they met.
And from the reporting I've read, it isn't actually clear if she was a spy (i.e. directly trained and employed by a PRC intelligence agency).
The details (businessperson working in a viable business) make it seem more like she was a willing asset, who likely had a PRC intelligence handler.
I don't think that framing helps him. He's one of the most targeted people in the world for espionage. If the claim is he didn't know, to not check the background of a prominent Chinese national with which he was having an affair is gross incompetence.