I think she’s the former activist, and the reason she “helped” the girls hide Soo Ho is because she also believed that he was an activist framed as a North Korean spy
And maybe the ANSP couldn’t use her equipment because the listening and recording devices are inside the dorm, so they couldn’t get to them? That’s a wild guess though, I have no idea how that technology works...
I don’t think it makes sense for her to be a NK spy. She could have revealed her identity to the other NK on several occasions. For example, she was alone with Gyeok Chan at least twice, in the bathroom and at the stairs.