These are heightened emotions in a tumultuous time Nick and Juliette were working with so hurt feelings wouldn't be unexpected but it has to work both ways. I've seen people argue that it was none of Nick's business who Juliette slept with while they were broken up even if one of the men was his boss and the other was someone gunning for his mother and him in the bed he and Juliette shared for years. If you feel that way, Juliette had no right to do what she did at the station. She can't claim Nick chose Adalind over her and go apeshit over it.
Personally, I don't have much of a problem with how Juliette felt but what she did about it. She basically turned into a scorned woman even though she was the one that broke it off. At that point, was it about Adalind having Nick's baby or what she did to her? I guess it's a bit of both but her having Nick's baby shouldn't be the reason Juliette wants to kill her if she's done with Nick.
Personally, I don't have much of a problem with how Juliette felt but what she did about it. She basically turned into a scorned woman even though she was the one that broke it off. At that point, was it about Adalind having Nick's baby or what she did to her? I guess it's a bit of both but her having Nick's baby shouldn't be the reason Juliette wants to kill her if she's done with Nick.