I have a little experience in this issue as I have met some Chinese women who faced similar experiences. Here are some possibilities:

1) She feels embarassed or disgraced as you mentioned and instead of taking the blame she has chosen to conclude that it was your fault. That you got her drunk and planned out the whole thing just to get her into bed. Maybe this makes her feel stupid and like she can't trust you because you "tricked" her. I guess you should take responsibility for the night and apologize if you did anything to offend her. This may not make any change.

2) As mentioned, she wanted to frolick with a foreigner and see what it was like and had no real intentions of moving further. She just wanted a taste of experiencing a different man and that could have left her with guilt. Maybe she somehow thinks she is betraying her son too.

How is it you went on FOUR dates with her and don't even know where she lives or where she works? Do you even know her name or her son's name? What did you even talk about?

Obviously, she could have felt like things went too fast and she made a big mistake which would support number one OR she didn't want you to know this information purposely which supports the second possibility.

I am leaning towards a bit of both so it's up to you to persue her or just let it go. In my opinion, I think its quite possible for you to persue. I would suggest the tatic of being interested in her son and talking about helping her son. This way she doesn't feel like you just want to use her for sex or something if she still feelts something.