Posting this for people who are confused about the drastic change in the drama's synopsis.
The original synopsis was wrong. 

The original synopsis incorrectly described the female lead as being married and having a child. It also said that in the end the male lead will help her get back her child from her ex-husband.

The female lead was never married, there was never a child.  She's an expert in Sanda, not Taekwondo.

My guess is that somehow the synopsis for a similarly named drama was added to this drama.

The current drama details are correct, and supported by people who have watched the entire drama and also by re-capping sites. 

I think it's more likely that the plot didn't pass the censorship board and had to change.  Xi Jingping has gotten very involved in censorship in the past few years, wanting to enforce stricter gender roles (no romances with divorced mothers) and of course more patriotism (no experts in the Korean martial art Taekwondo).

This drama has been delayed several times, so my guess is that it didn't pass the censorship bureau after it was first announced and had to be rewritten.

We're lucky it passed in its current form.