I already asked my friend and in the novel, Ang did intentionally do it to prove her point to Kobori.
Of course Ang would say she didn't "thang jai" (didn't mean to) because she regretted her actions. She's fierce, hot headed, and impulsive, but she's not a cold blooded murderer. In her moment of madness, she was so overcome by her anger that she took it out on Kobori......we all know that Ang does not manage her anger well and I still stick to the premise that her hormones from her pregnancy is intensifying her emotions and anger........all of her greatest fears are coming true in these last couple of episodes.....the return of Wanut, whom she can no longer give her heart to and with his return, her loyalty to her country is being tested and also her re-emergence of her hate for the Japanese.....for a brief moment, she temporarily forgot and sort of enjoyed being Kobori's wife.....
Although I sort of understand where she is coming from.......I agree with you Teedee, that Ang put herself in that position in the next episode. Why wouldn't Kobori leave?.........she screamed at him, refused to listen and reason with him, and used hurtful words that would make any man feel less of a man. When Wanut returns, she is so worried about him, that she forgets all of the sincere things that she has discovered about Kobori and pushes him too far.........Yes, I feel bad that she is hurting, that she misunderstood the situation and thought Kobori intentionally made Wanut's situation worse, but we must all own up to our actions........in the next episode, at that moment, she is the one who put herself in this prison of sadness.....and the only one with the key to her release is she herself....she needs to let go of her pride........and stop feeling so bound by her promise to Wanut that she can't accept the love that is in front of her.
The test for Ang is when she finds out the truth that she misunderstood Kobori. Will she let go of her pride and be courageous to finally except what her heart has been telling her or does she do nothing, feel helpless, not know which road to take, and just leave everything to fate and allow Kobori to relocate to Burma.
Yes, it looks like they changed it a little.....made her so mad that she threaten to do it, but at the last minute got dizzy and fell.....which makes her less harsh to the viewers and probably more fitting to today's audience because it's difficult to believe that any woman/mother to be would intentionally hurt her own child just to prove a point to her husband out of anger.