The evidence is instead of tweeting "I'm playing palworld" "I got tired of palworld" she's changing her steam name so people know what she's doing. And that she went from daily tweeting into disappearing for weeks on her PL.
They don't need access to it. They can just threaten her to stop using it. My bet is they already planned to when they saw the 15k tweet, but management took another week because they are just that slow at thing. Like how slow they were when they remember to fix the tweet regarding Pomu's vod getting nuked. Or waiting til last minute to announce Selen's not going to Anime Impulse.
Something along the line of "if you tweet more shit on your PL we gonna terminate you for real" or extending her suspension or whatever. They might even have threatened to legally sue her due to jp autism if she was already terminated. Everything is on the table when it comes to Riku.