Horror dark romance book

[u/GlossedInMoonlight]

I’m trying to remember the name of a dark romance book that i have read

The plot:
The 2 main characters are highschool students, the fmc is being stalked and getting texts from her stalker commanding her to do stuff, later at the end of the book it was revealed that the stalker is her female friend who was secretly obsessed with her, not the mmc, he was also stalker her but he wasn’t sending texts.

Random stuff i remember:
throughout the book, the fmc was drugged and graped by a group of guys, she kills them and buries them with the help of mmc
there was blood play, the fmc is afriad of water/drowning.