In Juliette's case, the problem was assuming Nick would act a certain way and taking preemptive measures based on that assumption instead of giving Nick the opportunity to prove her wrong. His love for her (or hers for him) was no longer enough to work through this latest issue. Nick said he would never hurt her but I don't think she believed him.
Adalind made the same assumption that Nick would hurt her but she hoped he wouldn't and believed him. That's it. (Edit: Typo, I meant to say...) Love was not an issue for them at this stage despite Adalind's feelings for him so she couldn't rely on a pre-existing loving relationship, in fact she had an antagonistic relationship with Nick almost up to Kelly's birth that should have made her extremely nervous and trigger happy to defend herself against him had she not trusted him.
Nick had reasons not to harm/hurt either hexenbiest, one for love and the other for his son's sake but the reaction between the two hexenbiest are as different as night is to day.
Adalind made the same assumption that Nick would hurt her but she hoped he wouldn't and believed him. That's it. (Edit: Typo, I meant to say...) Love was not an issue for them at this stage despite Adalind's feelings for him so she couldn't rely on a pre-existing loving relationship, in fact she had an antagonistic relationship with Nick almost up to Kelly's birth that should have made her extremely nervous and trigger happy to defend herself against him had she not trusted him.
Nick had reasons not to harm/hurt either hexenbiest, one for love and the other for his son's sake but the reaction between the two hexenbiest are as different as night is to day.