I’m not entirely sure of the plot, so I’ll try my best.
basically, a teen guy leaves his girlfriend, and sleeps with another girl. Guy decides to go back to his girl but the one night stand starts messing with them, I think he gets kicked out of school. The climax of the film is the guy and his girl shoot the one night stand, but the twist is it wasn’t her who was doing any of it but a jealous classmate of the guy.
I thought it was the Bella Thorne movie “You Get Me” but after viewing, it isn’t, but it’s along those lines and time frame.