There is a massive gap between where her ribcage ends and where her arm should realistically be, it's like a foot of missing rib cage there. Granted though I'm a bit baked out of my skull from a solid 8 days of retail work so I might want to call in somebody for a second opinion on this.
On here, I recommend you get the skull shape down first then draw lines for where the hair will go, including where the hair parts. You can then use this to sort of Hazard a guess as to how the hair will interact with each other. a good way to think of it is working in chunks, you can see this technique being used a lot in anime but it's essentially an abstract way of representing how hair tends to Clump together into thicker strands.
Another thing that can help is to find a picture of the hairstyle you want to draw on Google Images, or if that isn't feasible, try to look at how close a hairstyle you can approximate.
