How have they not figured out it is Jacob. Gah is she just stupid and Emma really should be smarter than to take jer to a party when she has a stalker like that I feel like Emma is just using Brooklyn's fame to party and have a good time.
Her sister is totally using Giroux to try to be better than her. I hope someone tells him.
Also, I think the stalker could be Jacob. He's got a thing for her and is clearly unhappy that she's back with Sid. He was so cool with it when she turned him down. And he literally knows everything about her, including where she lives and where she goes. He's got the means and the motive.