Very good narrative, maybe just a bit disturbing by the jump between the 2 main storyline Cecilia and Lydia.
Though, the 3 other review aren't really serious as I expect way better than the 4 and 5 they give you on the criteria BE Description and Characters.
For BE description, they are close to none.
All we get to know is that Cecilia get bigger and at some point she's exceptionally big, but we can't figure out how much.
Simply you never give factual detail, like cup size.
We don't even know what is Cecilia's starting size, or either her final size.
You don't give any element to imagine how big she is, other than 2 numbers at some point 36 and 44.
Which is, by the way, a complete error, as the number in measurement of breast isn't what will change if breasts grow bigger.
To make it simple, if breasts grow, it's the cup size that will change, not the number before.
So Cecilia could grow from 36A to 36C, then 36D .... 36HH etc...
But NEVER from 36 to 44.
The other negative aspect is Characters, we know nothing on them.
No background on Cecilia. We know barely that she hold her book shyly at start but that's all.
We don't know who she really is before changing, her taste, what she likes. Is she nerdy? Is she the cool girlnextdoor type?
Same goes with physical description, again, we just know she's a brunette.
Interestingly, you put a very intense effort in describing her different clothes.
Which is great too, but considering you give very few clear detail on physical appearance, so detailed cloths description gives impression you missed the point of what really should be worth describing so much.
Still good story overall