u/Emmi_meh — reddlx

I remember I got this book from the library when I was a kid & it was one of my favourites at the time, I've made a list of all the details I've remembered

It was part of a (4 book series?) about 4 sisters where each got their own dedicated book, at the time only 3 had come out, (I think) the MC of this book was the 2nd oldest sister
The main character & her friend were a female & in her teens
The cover was pink with the main character on it (Small compared to the writing) the main character had ginger hair (Potentially with bangs & some sort of blue/green top I may be misremembering that) & was drawn in a cartoon style
The main characters best friend, as mentioned in the title of this post had some sort of sleep disorder (I forgot the name of it) it caused her to always be tired to the point that she missed a bunch of school

I also have a few scenes from the book that I remember:

MC researches her friends condition & finds something online about of a man with the same condition talking about how his girlfriend just thought her was lazy
MC sees her friend with a boy at a cafe or something? (I think the scenario was that her friend had cancelled plans with her saying she was to tired & it turned into a confrontation)
The MC's friend had an older brother in college who had the bigger room, so the MC & her friends mother decided to switch their bedrooms so MC's friend would be more comfortable. I remember it involved painting the walls to her favourite colour

that's pretty much everything, If I remember anything else I'll either edit this post or add it in the replies, thanks

EDIT:

I read it some time after 2015 not sure of the exact year
It was a paperback chapter book, either small or medium in size
It was set in the modern time for when it was written (2010s I would guess)