Marinette could use her wits. If she's tied up, she might be able to find a sharp object nearby to cut the ropes. For example, if she's in a room with some old furniture, there could be a nail or a broken piece of wood that she can use.
Another reaction could be that Marinette pretends to cooperate with Adrien at first. By doing this, she can buy time and look for an opportunity to escape or get help. She might act as if she is okay with what is happening while secretly planning her next move, like leaving a clue for someone to find her or finding a way to disable Adrien temporarily.
Marinette can react by standing up for herself. She might confront Chloe directly and tell her that her actions are wrong. This shows Marinette's strong character.
Marinette could react with disbelief and assume it's some sort of joke at first. But when she realizes Adrien is serious, she might start to get really nervous. She could start fidgeting with her hands or her hair. If she's in the middle of doing something, like working on a design, she might drop her tools in surprise. Once the shock wears off, she would most likely be very happy and accept his invitation, but it would be a very flustered and excited acceptance.
Marinette might develop more empathy. Going through pregnancy gives her a new perspective on life. She may understand the struggles of others better, like those who are vulnerable or in need of protection, which could influence how she acts as Ladybug.
Marinette might start off as a scared and confused character when she first enters the League of Assassins. But as time passes, she would become more determined to survive. She would gradually learn the ways of the assassins and use her own unique skills to her advantage. Her development could also involve her becoming more assertive and confident in her abilities.
Marinette might be initially shocked when Adrien steps in to protect her. She could be very grateful and show it with a shy smile or a simple 'Thank you.'
Marinette's character can be developed through her angry outbursts. For instance, when she gets angry, we might see her make rash decisions that she later regrets. This shows her impulsiveness when overcome by anger. Also, her anger could lead to her learning new ways to control her emotions, which is a part of her growth. Maybe she starts to practice meditation or some other calming techniques, which changes her character over time.