Reddit reviews Eve

Might want to ask /r/YAwriters and/or /r/YAlit also.

While The Fault in Our Stars would be a good example of healthy relationships, I don't think Divergent is a meaningful pick if you want the main topic to be relationships and/or sex.

Some books that focus on context for relationships and sex instead of having it as a minor plot point:

• Forever by Judy Blume
  
• Two Boys Kissing by David Levithan
  
• Song of the Magdalene by Donna Jo Napoli
  
  /u/caseyoc's suggestion of Fangirl is another good one. Eleanor & Park, by the same author, is even more relationship-focused and building a relationship and consent is a huge part of the storyline.
  
  If you want to go off on tangents, Eve (terrible book) and The Jewel (better) are YA dystopias that deal heavily with consent and forced pregnancy. The Handmaid's Tale is a much better examination of the topic and accessible for high-schoolers.
  
  The Girl of Fire and Thorns trilogy by Rae Carson and the Trickster books by Tamora Pierce also win kudos for the protagonists choosing to have sex in a healthy relationship, seeking out birth control, and waiting for it to take effect. Both are in a fantasy setting where this problem is commonly brushed off.