Always nice to see a new writer dipping their toes in the water, especially with gentle growth stories. It seems like 80% of new content is shrink stuff nowadays and only a minority of the growth content is gentle. I've written my fair share of non-gentle content to help me develop as a writer, but the gentle stuff is my favorite thing to read/write. 

Now for the review: 

Your writing fundamentals are solid. The grammar, pacing, and early characterization are all great. So long as you plan out your chapters beforehand and don't write yourself into a corner, I foresee this being a great story.

Truth be told, there are a few minor errors. A missing hyphen here; a misused word there. There were several instances where you reused verb phrasing, which is not technically incorrect but it does read somewhat awkwardly. 

All of that said, this is your very first story and I made all of these very same mistakes a year ago when I started writing. I still catch them occasionally in my third or fourth proofreading, so it's by no means a mark against you. Just keep writing and everything will improve. You're already in a fantastic place and these very minor mistakes are perfectly normal. Professional writers make them all the time; you just don't see them because editors usually catch them first. If anything, these things just confirm that you're a person with a keyboard and not an AI. 

I look forward to seeing where the story goes next. I had a similar concept for a short story called "Anxious Expansion" (which I have not written), but I'm eager to see another writer tackle the premise in a longer-form narrative. The first chapter has already intrigued me and shows a lot of promise. For instance, Ro's professor (and presumably the school at large) doesn't seem to know about her affliction. It also seems that the condition can lead to a positive feedback loop, whereby her anxiety makes her grow and her growth makes her anxious. These details are great and invite further explanation and hijinks.

Finally, a bit of housekeeping since you're new:

This site is rather archaic. Depending on the word processor you use, it may not save text alterations like italics or bold font when you paste your story, so you might have to edit that manually within the site's text editor. I'm only saying this in case you used one of these alterations and didn't notice they weren't preserved when you posted the story (as I hadn't when I started posting).

You have a few useful options in your "account info" panel under "edit preferences," which I would recommend activating. Most of them are self-explanatory, but there is a question mark next to each one with further information.

Finally, there are two "delete" buttons below each review. They are bugged and only serve to delete the review itself, not your reply. Don't use these delete buttons unless you intend to delete the review itself. Just proofread your response and accept that once you post it: it's out there. 

Welcome to GTSWorld!