BAY, I kept thinking, "WTF?" Let's just toss her into the deep end when a massive amount of freakin' zombies are running around. YEAH!
They go from, "OMG Juliet! You got a cat scratch! You are so fragile!" to "Yeah, come along! You're a veterinarian!"
She's essentially going from being the "one who can't know about the Grimm thing," to the damsel in distress.
Nick wasn't pleased about the idea (all over his face), but he didn't want to flat-out tell her no since they've just gotten back together. Rosalie was being her usual nice peacemaker self and Monroe will defer to Nick publicly. I don't think this will be a habit, not without giving Juliette some training.
Notice in the scene the body language and tone of voice is awkward. They're all trying to not treat Juliette like a child.
Boyfriend-Nick was between a rock and a hard place on it, though. How do you not get newly-reunited girlfriend mad at you? Telling her to stay behind or go home while Rosalie goes doesn't
look fair - they're both women of about the same size.
Now Juliette has seen how dangerous Grimm life can be, she'll either be scared straight into staying home, or she'll study to be a contributing part of the group. Nick's going to need help getting home from, so everybody's going to have to be part of the rescue.