If you scroll down to 2018-06-08 on this board, you'll see my thread titled "The many deaths of Julie," and the story you mentioned is in that thread. It does feature lesbian sex and a very brutal murder, although the killer is an enraged and drunken boyfriend, not a lesbian.

Oddly enough, I am in the process of typing a story that does feature exactly what's in the title of your post. If this board doesn't crash again, you might get to read it. I intend to post it in my Julie thread when it's finished.