YA Semi post apocalyptic world after a disease killed all middle aged people

So it is Fiction.

The Plot is that this teen girl who is living on the streets like almost every other young person. She is taking care of her sibling and agrees to use her body to earn money and food for her family. They did her all up and made her perfect.

Then they market her talents for any old person to temporarily take over her body and enjoy being young again. Her special talent is the use of fire arms. She is a really good shot. An old woman rents her for a bit to assassinate someone. Then a whole adventure starts. It has a bit of romance too.

I read this book when I was a freshman in high school which was 2015.

The cover of the book had the title of the words used for the children at that time in the world.
The book was ment for high school kids. That's all know.

Thank you for your time. :)

Starters by Lissa Price.

Thank you so much! Hope you have a good day!❤🖤❤🖤❤🖤