A lot has been made of a graphic/chart she posted about her books and age ranges.  While helpful, everyone should keep in mind that Colleen Hoover is definitely an ADULT author.  So like any adult author, you have to decide about content and if there is enough crossover appeal with high school students.  Obviously, many other factors go into those decisions when developing a collection - like the age range of high school students.  Many of my freshmen are 13.  I would definitely not add her books without reading them first and making those decisions for my student body and my community.  I do tell kids to head to their public library if they want to read something we don't have - and I had a senior talking to me yesterday about just starting It Ends With Us - definitely not one I would add to my HS collection!