I feel that, yes Taew's MM is cold, but she seems to be warming up to JN. In the first episode she mentioned something about promising her uncle to never show her tears to anyone. For MM to cry in front of JN is saying a lot already. She is showing a lot of her weak sides to JN. I can see her character develop from this cold person to a person who is curious about western culture and then actually seeming to care a little about JN. I mean if she didn't really have the heart and was still all about duty, she would of listen to her brother's request to poison JN. But what did she do, throws the poison away. It's sad that she is stuck between duty to her home land and duty to her husband. I can see that this is the first betrayal towards her country. I feel having a western doctor check up on MM is a way to show her change as a character, because, to me, I think this is a way to help show her that change is not bad but good. Being westernize not only helped make things useful, but it can also help during times of needs, in this case, MM's time of need is when she thought she lost her baby. Then finds out that the western doctor helped her through the process of caring and securing the safety of the baby. She is slowly caring for JN little by little, even though she doesn't recognize that JN loves her a lot by being affectionate towards her during her times of need.
Well said. If I could give you two thumbs up in the comment rating I would
. I am actually watching this raw without any understanding of the language (actually I could pick up like maybe 5% hahaha some words are almost exactly the same as my native language). But I could definitely see characters development from MM side. It was frustrating at that start to watch her so stubborn and cold (but somewhat understanding) but there has been a a few scenes that proves she had soften up when she spoke English to JN friend and shook his hand which she had refused to do at the start when they first met. The turning point for MM was definitely when she was close to having a misscarriage, you can see her characters changed from being completely stubborn to being somewhat soft and possibly developing some trust for JN. And you are right, if she was completely cold and was all about duty she would have definitely poison JN.
I don't feel MM even considered killing JN, she had always intended to throw the poison away from the start and was more conflicted about her feelings of how her brother would take it when he finds out she didn't do as she was told and this would definitely be seen as a huge betrayal not only to her country but her beloved brother. JN is fully aware of MM commitment and dedication to her country/people and family. So for MM to not go ahead with killing him as requested by her brother to do so (remember MM love/listen obey her brother) her decisions to not poison JN is a huge betrayal to her country and family and is also the first step to proving her love for JN is much stronger then any duty that had been given to her to fulfill and I believe JN knows that MM deep down loves him too now. This is why he said to MM according to the translation from banmarkpantip_inter
Sukawong)
“... Because I know that your love for me is real.
It’s not a trick to push me into your plan.
I’ve never think that you will be able to kill me.
BUT,
If everythink I think was wrong,
If I am going to die,
I won’t be angry at you.
I won’t blame you at all.
I am ready to die by your hands,
the hands of the one I love most in my life.”
Just relax.
We both have duty for our own countries.
Till now, I don’t think it’s too late for your father and brother to accept the fact,
and not think too much on their side.
.
You,too.
If you put away your duty,
I would have heard the ‘love’ word from you.”
I am sure that MM deep down also is somewhat aware that JN loves her a lot, but she just don't want to accept it because to her she believed that it will never work out due to the reasons that she was married off to JN as a duty to serve her country and felt pressure from
her bother that once her duty is done she is to leave JN and come back home. So to protect herself MM builds a barrier between her and JN hopefully she won't get hurt any more then she is now when the time comes.
. 
One of my favourite scenes by far. translated by banmarkpantip_inter .
