I just finished watching ep 3 and 4.
Since I haven't seen ep 5 yet, I can't say much about the other sisters, but yes Khun Ratt was naive and she followed her heart but I wouldn't say that she deserves the bad things that Pakorn is doing to her. No one deserves to be treated like that, no matter how stupid or how naive you are.
All of us, especially women, we enter a relationship/marriage b/c most of the time we follow our hearts, b/c we are in love. Some of us gets lucky and we find men that love us as much as we love them and the marriage lasts a lifetime. Some of us willingly go into it with good intentions but along the way one of us changes and it ends in divorce. Then there are some of us who are like Khun Ratt that are inexperienced in judgement of character and we realize when it's too late that we've made a big mistake. No matter what fate has in store for us, we all deserve happiness and people who will love us. No one is wrong for following their heart and true love really does conquer all like Khun Ratt says. The only problem is what she has with Pakron is not love. He tricked her into empathizing for him and getting her to fall in love with him.
If we didn't see this story from all angles, we too would think that Pakorn is good person. How can anyone who takes a chance on love deserve the bad things that comes with a false love or a love that wasn't meant to last?
She made a mistake, but who hasn't. I hope that she will learn from it and somehow get herself out of it. Although, it's hard now b/c she doesn't have the support of her family.