Hi hi! Sorry I'm late to respond!
let's jump right on in!
overall, I liked it! The tone was that of a happy coming of age YA. That being said, overall it was very low stakes. no conflict was introduced. more on that in the specific details
Seventeen baby-blue lit candles were haphazardly stuck on top of it, as it sat on the centre of the table waiting for the birthday girl Kacey Langford to blow it out.
I like the image here, but I'd fix up the sentence structure. It reads a little clunky. Maybe something like Seventeen baby-blue candles had been haphazardly stuck on top of it and it sat now on the centre of the table waiting for the birthday girl, Kacey Langford, to blow it out.
She was surrounded by her family; her parents, Benjamin and Gina - actually smiling at Kacey, for a change -; her older brother, Wesley, who had just come home from university to visit; and her younger sibling, J.T., who was hungrily looking at the cake whilst licking their lips.
So this is where a little bit of conflict is introduced, but it's done only through telling. Kacey is just telling us that her parents don't smile at her, but here they are, smiling. It would be better if they weren't. Why don't they usually smile at Kacey? You need to explore that a bit better to get tension in this scene
(half because of her dyslexia and half because she couldn't be bothered)
I like this little aside, and it's telling us more about the protagonist, but you could go for even more ~flavor. Show us a bit more of Kacey's personality, because she is the narrator, right? If she was a little bit sarcastic, you could go with something like some people would say it's because she had dyslexia, but Kacey maintained it was because it was a stupid subject
(not counting Yannika Harding, who always had it in for her for some reason)
So Yannika being good a tennis does not necessarily mean that she has it out for Kacey, so you need to seperate those thoughts. In fact, just introduce the name Yannika Harding now, and cut out the part about her having it in for her. You can introduce that when they meet the first time. you could talk about how Kacey wants to beat Yannika, which could also add to the tension.
It's your last year as a teenager so make it last!
aren't 18 and 19 teens too?
She dumped the presents on the sky-blue cotton duvet of her bed, and tore into them with the same childlike glee she kept since she was a baby.
This just comes across a little weird that she'd open her presents alone. shouldn't she open them downstairs to where her brother and sister, if not her parents, could see?
She got up and walked over to her white floor-length mirror, inspecting herself.
ooo no…so this is a cliche that most people would tell you to cut out. the paragraph introducing how she looks by looking in a mirror all in one big dump. try and steer clear of things like this and add in description like you did at the beginning with her hair, just woven into the story.
I think you could improve this with a bit more conflict with the parents, but overall super nice!! I think it has the potential to be a really fun story! Don't hesitate to ask me questions about my comments or post more or anything like that! keep it up and keep writing my friend! :)