Yeah, like… exactly what she's doing? People here are so willing to assume that she's doing all this out of self interest, because of what? A $500,000 book deal? Compared to what she stands to lose? She isn't stupid, she knows the risk. As a New Zealander myself I'm not sure if there's just some cultural difference at play here with the tendency to assume the worst in people but it seems kind of sad.
Looking at the CSS variables page it seems that this is because they scale up the base font size at various breakpoints, starting at 106.25% at 576px, and going all the way up to 131.25% at 1536px. It definitely feels too heavy handed to me. The first time I viewed the website on mobile it seemed fine (because it's actually at or close to the browser's standard font size) so I wasn't sure what the problem was until I viewed it on my desktop. I can kind of see what they're going for as it keeps the layout fairly consistent, but I don't think it's the right approach.
And from the dev's followup explanation it just feels like their default is that everyone is entitled so they react accordingly. That response sure came out of left field, and I think the dev is lacking a little self awareness. Taking a defensive stance from the beginning is just bound to cause unnecessary drama.