After another death at Eaton Place, Victoria wonders if the family curse is real. [This is vague. Does she suspect that it's real, or fake?] When the young funeral photographer [is Vic the photographer? If not, change it from 'the young' to 'a young' or just cut it altogether.] sees a ghost, Victoria
starts a scientific quest and uncovers a plot [to do what? good place to introduce stakes] against to murder her father and the industrialists at The Great Exhibition. #PitMad #MG #YA #F #UF #HF
Agree with giffordmac, what's at stake? Also (at the risk of showing my hashtag ignorance), why do you identify the story as Middle Grade, Young Adult, Fantasy (or fiction?), Urban Fantasy, and High Fantasy (or is that Historical Fiction?) Wouldn't it be better to actually identify the genre of your story and stick to that?
I'm only vaguely of aware of "Eaton Place" and "The Great Exhibition" so it won't convey the setting as well as you'd hope. Sure, google might clear that up in a second, but you want the hook to be self-contained. If a reader needs to google something to understand your hook, they'll probably just move onto the next one.
As indicated where I hacked up the hook, I'm not even sure who Victoria is supposed to be.
Another thing that confuses setting: The camera wasn't invented until 1885, and "The Great Exhibition" was in 1851 (according to the google). So Victoria couldn't have been a funeral photographer at the time.
Ok, so that's heavy on critique - and my own misunderstanding. Here's attempt an actionable hook in hopes that it helps convey a path to a solution:
When the ghost of a murdered guest appears to Queen Victoria, she orders an investigation that uncovers a sinister plot to derail the Great Exhibition of 1851. #YA #HistoricalFiction
Hope that's useful!