Ok let's humor the idea, that she is really making her own campaign ad and not lying about that:
In that case, Frank letting Brianna make her own campaign video, instead of paying a professional to do that for her, is another hint that Frank is either truly a mad mastermind, who wants to see Brianna crash hard or he simply doesn't really give a shit what Brianna does.
While Brianna may be the poster-troon for the Dunning-Kruger-Effect, Frank is certainly not (except when it comes to his writing, I guess). No matter how thick his rose-colored glasses are, Frank should know by now that - without a fuckton of people doing things for her, and helping her out - Brianna is not just going to fail, but to make an ass out of herself in eyes of the wider public. And even with a fuckton of helpers and advisers, it is not guaranteed that she won't. At the moment Bri can still tell the 'press', that all the bad things you can find about her on the internet are GamerGate-lies. But once her escapades manage to hit the local newspapers in Boston, the entire area will laugh their asses off, when they see her on the streets.