I don't remember the last time I read this book so I only have limited information.
It was about a girl who had powers to control darkness/night. At the start of the book, she ran away from her home with 2 twins (who later in the book get the abilities of water and fire) and another person that I think is a boy. Anyway, while she's running away she dislocates her shoulder jumping of the town/village wall but manages to getaway.
Later in the book/s (I don't remember if it was one massive book or separate ones), she learns to melt into the darkness when she's being hunted down by the evil people.
Just to be clear: Don't know any names of the characters, don't exactly remember when I read it. Pretty sure the age of the characters was in the 13-17 age range.
If you don't know, it's a fantasy book about a girl who goes on an adventure trying to master her skills and be able to fend for herself. Now that I think about it they received some sort of tattoo that marked what ability they would eventually get when they reach a certain age.