Underground society tested every year for powers

[Sydney]

Hi so this book is about a girl who lives in an underground society because above ground is a wasteland. There is constant newsfeed showing how terrible it is above and everybody wears grey I think. Every year they are tested for something and at the last one her bf or guy best friend tests positive and is sent above ground. She fakes a positive to be sent above ground. When she goes above she finds that it is a city where everyone has powers. The city is divided into 3 segments by powers. One segment is for those with minimal or no powers and it has extreme poverty. The segment she is in is the biggest and most normal. The final segment is for the most powerful and is dangerous; there is a bridge connecting the middle and powerful segment but can only be seen by the most powerful. She eventually gets sick because she doesn’t have powers and can’t survive the new toxic world so she gets tested on in the poor segment. This causes her to gain the power to absorb/ learn any power and she eventually escapes. This is all I can remember, but it was a good book and any help is welcome!