Natasha Friend.
Titles I've written about:
My Life in Black and White (2012):
Kudos to Natasha Friend for the best friend storyline, too: Lexi is angry with Taylor for hooking up with her boyfriend, but it's about the betrayal more than anything else. She doesn't stoop to slut-shaming—even when her mother does—and even more impressive, when Lexi has an opportunity to stand back and let Taylor's own choices result in what some might term 'just desserts', she does the stand-up thing. It's quite satisfying, and again, rings true.
For Keeps (2010):
If you like Sarah Dessen, I'd recommend that you pick this one up, despite the (I say this in retrospect -- while reading I enjoyed myself so much that this didn't occur to me while reading) Days of Our Lives-ish-ness of some of the plot twists.