She follows Jack so, unless she's muted Jack, this is all being beamed directly onto her Twitter timeline.
I think the issue here is that Jack has turned herself into one of those Twitter personalities, a bit like Matt Haig, where people who are at a bit of a loose end when they first join the platform follow them because they think it's some kind of unwritten rule that you have to. Then of course she's had the odd tweet that gains a fair bit of traction because she's good at being angry in 280 characters and people follow her because a follow equates to showing that you also hate the Tories. To the uninitiated, she's typecast herself as a whistleblower on these sorts of issues. It only takes a close reading of her tweets and actually following her account (and not just brushing off moments like what we've seen today) to understand what she's like when the mask slips. Unreal how more people haven't unfollowed her, especially given how others like Marcus Rashford have a) done more and b) don't tit on the people they beg to help them.