Once she announces it in the media, wouldn't it be a professional policy opinion? CEOs are similar. They can believe what they want, but what they say to the media can be punished (like Elon was). The real sticking point is how is she of one opinion then flip to the complete opposite the next day without giving a reason. If they have to report their intended trades then it could avoid this short term play.
Spouses and household members are held to the same restrictions as the regulated individual, regardless of the conversation or not. The only reason it's hard to prove is because they are in a position of power. The SEC would jump on any normal people doing the same thing.
Again though there's plausible deniability, as you say. It needs to just be outright banned.
The problem is in the grey areas. Take the Pelosi example. The material nonpublic information was her personal policy position. Assuming she acted purely venally, are your own intentions insider information? If I know I'm going to get Chipotle for lunch tomorrow, is it insider trading to buy Chipotle shares?
If, on the other hand, her husband took a conversation he had with her about policy and then traded on it, that would be insider trading. Unless they did it over text message, however, the odds of proving it are zilch.