Great ideas, execution needs work
There are clearly some really great, creative ideas that drive this writer, and the images that explain the magic are a great way to start off. However, I found my mind wandering a lot while reading because the flow and atmosphere of this story is off; it reads like a summary in some places, then jumps into dialogue that does what is called "info-dumping", where the background and world-building information is all thrown at the reader at once. I found this to be difficult to follow and too much to take in, but the ideas themselves are very interesting and the entire thing could be easily improved by spreading out this information throughout the story. For example, rather than have all the creatures of the world all revealed in dialogue, I suggest that the writer has their main character learn about the creatures along the way, or a few at a time when they become relevant. I get the feeling that this writer would be fantastic at doing world-building for RPG games, or creating encyclopedias and bestiaries for their worlds, but I think that when it comes to including those aspects int an actual story or novel they need to try a different technique. It might even be the case that they are simply super excited about the information they've created and are really eager to share it with the reader, so they wove it into the story like this. This actually happens to a lot of writers (I'm guilty of it, too), and so I suggest taking highly detailed notes and compiling encyclopedias for yourself to get it out of your system, then afterward, carefully pick and choose what should be included in the story and when. I've had to do this too, and it makes everything much easier to read and so much cleaner as a written work, it's just hard as heck because it feels like you're hiding away your gems and not showing anyone. But a good writer always saves the best gems for the time and place that will make them shine brightest :)
Read the story now
The other big problem I had with this story was the punctuation for dialogue. This is not the first Inkitt story I've come across where this is an issue, but this was my #1 thing that made it difficult to read, so I wanted to point it out to the writer. When a character speaks, and their line is followed by "[name] said/asked/replied" etc, the dialogue right before it should never end in a period. It should always be a comma. For example:
"I told you Rosetta." Jay replied. "I knew it would make you feel bad." should be:
"I told you Rosetta," Jay replied. "I knew it would make you feel bad."
This doesn't seem like a big difference, but it's crucial for your work looking professional and also for the flow of the story. When the reader sees a period, that's a full stop, but when a comma follows the dialogue line, it flows better into telling us who is speaking, and this or an ellipsis (...) are the only correct punctuation there. There are times when dialogue ends with a period, though, and that is when, rather than the text telling us who is speaking, it implies who is speaking by using an action, or a "beat". For example you could change the above to:
"I told you Rosetta." Jay was wearing a self-satisfied smirk. "I knew it would make you look bad."
Or, for a totally different sentence re-imagined:
"What a cute little boy, bossing me around! I think it might be fun to use magic!" Rosetta giggled and jumped out of her bed, surprising the patients in the room. "I'M GOING TO LEARN MAGIC!"
^--You could just put that all together rather than break it into two paragraphs, and use capital letters to show she's shouting rather than telling the reader.
Another thing about dialogue: Try not to give a really long line of dialogue, either a super long sentence or several sentences, and only THEN break it up with "[name] said". I absolutely love the Harry Potter series but that's actually my biggest gripe with it, is that, when there are 5-10 characters in the same room, it lets you read a huge line of dialogue before bothering to tell you who's speaking. Now, your story was actually better than that because for the most part it was only Rosetta and Jay speaking, so you could follow who was who as it goes back and forth without too much confusion. But for example, having a big long paragraph and then at the end saying "Jay asked" is unnecessary because we already know he's speaking and the line ends with a question mark, so all the dialogue tag does is disrupt the flow.
And lastly, one final tip: When using dialogue tags ("said', "asked", replied" etc.) try to stick to "said" as much as possible. Even if someone asks a question, you can sometimes use "said" if you don't want to interrupt the flow, because "said" is practically punctuation in the sense that it doesn't distract the reader at all; people's eyes skip right past it and their mind stays hooked on the story content. But when you have lots of "exclaimed", "asked", "replied", "pestered", etc. the reader starts to see those more than the actual line being spoken. You should use those to break monotony ("said" does get boring) or to clarify or for emphasis: So for example, "exclaimed" can be a good way to show the character is speaking louder than usual, if it's not already evident, or that they are always excitable but that only works when other characters are sticking to "said" and "asked". Don't over-use it or it loses all of its punch. Meanwhile, tags like "pestered" can almost always be gotten rid of: Show that she's pestering him through the dialogue line itself, or through her actions; make her put her hands together and beg, pull on his arm/sleeve, or ask incessantly. But have her "say" it, not "pester" it :)
I would love to see the write go back through and clean up the first chapter of this story. These ideas are so creative and interesting and deserve that kind of attention from them. I also hope they don't mind my review/critique, as I am earnestly just trying to help. Thanks to the writer for putting their work out there because that takes courage. Never stop writing!