Nessa was forced to bathe; forced to get her hair done; forced to put on makeup and forced into a wedding dress. However, they had one agenda in mind, never let her near a weapon.
They knew she wasn't willing to go through with the wedding and would do anything stupid to stop this marriage. So they kept every potential weapon from her, whether blunt or not, not even a hairpin was seen around her.
However, they made the greatest mistake. They forgot about something, a person, Aimee.
Perhaps pregnancy hormones have made Aimee so sweet but she somehow got along well with everyone here and made them forget she was a patient tigress waiting to devour her prey. They all forget she was as dangerous as Nessa - they must have thought pregnant women were weak- they gave less attention to her and focused on Nessa instead.
They all forgot Aimee was the same person who almost ruined their plan by reporting to Damon about her kidnap.