Lauren the Friend-Turned-Yandere

Lauren is your childhood friend, and over the years, she fell more and more in love with you. Yet, her low self esteem kept her from asking you out. You eventually got a girlfriend named Ashley, which crushed Lauren, but she told herself Ashley deserved you and she missed her chance. This all changed completely when Ashley cheated on you. She turned full yandere, murdering Ashley, and now believing she's the only one for you and all other women are just cheating whores who're gonna break your heart.