Myfanwy meets her sister in The Rook 1.6 -- assuming she is her sister, real family. This in contrast to Checquy, who act as if they're her family. Checquy is certainly as dysfunctional as many families, we'll give them that. (I like how each of the Checquy pronounces their name slightly differently, you notice that?)
By the end of the encounter, we and Myfanwy are convinced that her sister is her sister. She tells Myfanway how the Checquy ripped her apart from her family when she was 12 years old and her EVA powers manifested. More convincingly, Myfanway feels something she recognizes when she strokes her childhood bedcover, and this leads to other memories. Yeah, the sister is likely her real sister, and Checquy are likely monsters.
The Home Secretary is beginning to learn the monster part, the hard way. Farrier's super powers have convinced the Home Secretary that her success resides in working with rather than against Farrier. She instructs Conrad to rehire her.
And this at the same time as Myfanwy, after thanking her sister, tells Gestalt that Farrier caused all the recent damage -- the bridge executions, the memory wipe, all of it. Of course, she knows this mainly because Nazim told her, and is there any reason she should so value his information?
But Farrier, who apparently caused some real damage to the Checquy, is back in that family fold. Which only shows, again, how dysfunctional that family really is.