The Meaning of Birds by Jaye Robin Brown
Jess is still kind of a mess when she meets Vivi, betweem grieving the death of her dad and trying to cope with her anger at classmates who harass the "gay girl". But Vivi changed all that. Vivi doesn't just love Jess, she also encourages Jess to pursue an artistic future.
And then, suddenly, Vivi died.
Reeling from loss, Jess retreats back into old (bad) habits to cope. She drinks, she skips schools, she gets into fights, and she throws out her art portfolio--because art reminds her of Vivi, and Vivi is dead.
The narrative skips back-and-forth in time, from scenes labeled "Then" featuring Vivi and Jess together, before Vivi got sick, alternating with scenes labeled "Now", when Jess tries to figure out how to think about her future.
This compelling story features flawed characters, including Jess and Vivi, and also their friends, families, and teachers.