I’m looking for a book I read in High-school (2011) I believe the book was written and or published 1985 to 1999.

Keywords: YA romance, senior year American high school, new girl, friends boyfriend returns from a semester abroad, new girl falls in love with friends boyfriend.

Summary/synopsis:The book starts out with a main female protagonist who was new that school year. The setting is high school, in the autumn/winter. She goes to school and talks with her new friends and finds out that one girls boyfriend who is returning home from a semester abroad.When the boyfriend returns, he’s very welcoming and excited to talk to everyone again but it seems like everyone is treating him very similar to the way he was before he left. He wants to talk about his new experiences and the only one who can relate to is the protagonist as she had family in the part of England that he visited. They talk about the old stained glass windows. Later it’s apparent they like one other a bit to much. They are hanging out together but during one day, it is too much and they talk about his feelings for the main character in his car. They decide that they should put distance their relationship so as not to be unfair to his current girlfriend until he breaks up with his  girlfriend to be with the main character.Somehow the friends catch wind of this and assume that the main character and boyfriend were cheating more than they did. The Ex girlfriend and main girl get into an argument and later at school the friend group is mad at both of them but the two main characters support one other through this until the friends realize the main characters were sincere and tried to make the most out of a hard situation. I believe it ends with talks on them going to college potentially together.

Other details I remember: they held hands in the car and the main character noticed the boyfriend’s thick healthy nails.The main character was a brunette.The ex girlfriend was blonde.The boyfriend played a sport before going to England. 
I can work out more information if I can, but I don’t want to Mandela effect myself more than I may have already done.