If she were to short the stock and then posted a tweet is that illegal? Or the inverse if she bought the stock and posted a tweet? It seems like some of these social influencers have a lot of power.
Ethically, it might be nice if she disclosed a position, but she's [presumably] not a financial analyst or advisor, so she's got no duty to disclose.
I mean, if you were president, you could make good money for yourself and your friends just telling them which way you were going to tweet about a company a few minutes before you do -- if you didn't care about the appearance or ethics of it...
I'll go out on a limb & say you're not a lawyer.
How do you arrive at calling Kyle Jenner vacuous? She has an audience and has been quite successful at monetizing. If she is vacuous then Snapchat and lot of other startups should be described the same way. Given the sales of her cosmetic line, a Wall Street investor would do well to listen to her when she thinks a service is over.
Whatever made that legal must make what you propose legal too: after all she could say "I shorted the stock because I thought it was doomed; I shared my frustration on Twitter out of the same frustration."
That's quite hard to separate from "I shorted the stock because I knew that I could manipulate it into falling by tweeting a negative opinion about it."
There is a difference between insuring a house you want to live in and insuring a house you want to burn down.