Theories on Ms. Pi?

Idk who she dated back then but seems so sus ,also seems like she has some kind of a connection to North. She is taking care of Bunok cuz  her teacher (I think Bunok's father or sister) asked her to do that. Also seems like she knows all the  backsotry behind Bunok and her sister as well. My guess is maybe she dated some high profile guy from South . Both of them used to be activitists against the government or something and after seems like they fled to North but got caught in the process or afterwards and idk how she gets linked to Bunok or sister. Or else she used to be an undercover spy in North idk...she is the most mysterious character in the whole drama.