These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Creator's Pet: Given how the whole book seems more dedicated to her unremarkable coming-of-age story, while reducing iconic heroes to voiceless extras with no development, Bertie was bound to be this from the get-go; despite being the main character. Readers looking for an inventive plot involving tragic heroes and archetypes will probably end up being irritated by some bratty teen whose relevance to the story serves no justifiable purpose.
Mary Sue: Bertie's role as some random girl among an assortment of Public Domain Characters bears an striking similarity to self-insert fan-fiction. Right down to the original character being inexplicably related to a well-established, popular character and hogging page time from all of the prominent, but mostly anonymous, figuresuntil every relevant plot point or character motivation leads back to her.
Unintentionally Sympathetic: The Stage Manager in "Eyes Like Stars". For all intents and purposes, Bertie is the one readers are expected to side with while opposing him whenever he flips out on her for causing trouble. He's the bad guy for being happy that the girl who wrecks so much havoc on his theater (and livelihood) may finally be getting some comeuppance and get kicked out for good. Yet, the narrative treats him like he's a huge jerk who's reasons are completely unfounded and even deserving of grievous injury...