How did Nanna's mother know... SPOILERS
... that Nanna worked at the same night club as her sister, Charlotte? In S01 E10, Nanna's mother opens a Christmas card addressed to her daughter and it somehow reveals that Nanna worked at the same night club as her sister. How is that?
Also, why on Earth would Charlotte wait 10 episodes before bothering to mention to her sister that Nanna worked at the nightclub and met a bloke there? She knows there's a murder investigation on. Didn't she think this might all be highly relevant?
Apologies if I am being stupid. Just a very quick explanation will be fine :)
Thanks