Help! I need help brainstorming ideas for a murder mystery plot!?

we start out with a detective's aunt in a modeling company's meeting. there are two models who are best friends but from rivaling teams in the company. nikki and allie. they have picked, previously, allie as the model on the billboard but suddenly at the meeting the C.E.O changed his mind and picks nikki. nikki seems persistent not to take the job, but allie claims it is okay. we then, over time, see the manager (not the C.E.O) of the job flirting with nikki, furiously she denies him and slaps him; in return he slaps her and looks extremely scary,murderous almost. *note, please foreshadow (when the authors hints what is going to happen) it so it is hinted he might be murder worthy.and then so we see other models from another modeling company (giving her dirty looks) *also foreshadow they might be murder worthy, the models. the next day it is seen that allie is crying over the now dead nikki who has jumped down from her building. it is then the detective enters the story line. he does not think it is suicide despite the fact the cameras showed nobody else going into her building or any traces of a 2nd person in nikki's home. at this point you should write whatever you want, more foreshadowing, murdering clues, or whatever. so then at the end they discover allie killed her in jealousy, thinking nikki sabotaged her chance at fame when really she was helping allie. allie tied nikki's hair in a braid when she was drugged and hung her body across the opposite building so when allie cut the strings nikki's body would fly down, suicide being the first thought comes to the others mind. allie then kills herself/or jail sobbing that she can't live with herself and it is panned into the sunset, the detective doing a signature move and his silhouette disappearing into the shadows.