It’s just lolita for the fashion style, gothic lolita is a substyle of the wider lolita movement which has other substyles like sweet lolita and classic lolita that each try to focus on particular parts of the overall aesthetic of cute, frilly, victorian-inspired clothing. The vtuber is very much not wearing anything even remotely lolita, the outfit lacks pretty much all of the characteristics beyond just vaguely being cute.
Ultimately the names for all of these call back to the novel Lolita, since in Japan the term became associated not with the pedophilia that is the focus of the text but instead it kinda merged with pre-existing idealised notions of cute young girls to the point where, over time, the term has been basically entirely disconnected from its source material.
Lolicon reintroduces the sexual component through the addition of ‘complex’ to the overall term. Technically there are non-sexual ways to understand it but like you said, it’s mostly awful pedo stuff. The vtuber here is specifically saying lolicon. (ロリコン is rorikon when transliterated)
Source is my obsession with lolita fashion and my little bit of self-taught japanese.
It’s outright my favourite manga, it manages to avoid most of the issues fantasy manga tend to fall into nowadays and it’s remarkably mature and well-thought out in how it approaches a lot of its subject matter. It’s also just a delight of a work when you analyse it.
Since you’re quite early I’ll go over one of the simpler things I had fun considering: the magic system! Without going too in depth, it functions as an allegory for several things at once, most notably art. Obviously the magic is drawn, but it goes further as the way that the witches relate to their magic is the same way artists relate to their art; they develop styles and preferences, they have to work around their lack of skill in certain areas to produce their art, the way people talk about it, etc…
But it also doubles as an allegory for scientific progress, one of the forbidden magics is medical, after all. And there’s this lovely tension between the two. I’d go further but to really explain my thoughts requires a lot of later context.
It’s a lovely series, and I adore it.