My DSD is 11 and has always since I've been in her life (5 years) listened to adult conversations, I don't know if this is normal but she takes a lot of pride in knowing exactly what's going on with our relationship and within the house in general and it's often made me self edit when she's here (40% of the time)
For example I might mention to my DH I need to book our dog in for a teeth clean and she'll ask the next time if rufus has had his teeth done, sounds innocent enough and maybe it is but when its frequent comments all through the day it does become wearing. I must also point out these often arnt family conversations, she over hears us talking whilst we cook dinner or load the dishwasher and she sits listening.
We were at a family party last weekend and my sister had a drink earlier to toast the occasion, small glass of fizz, when my sister got up to leave (bearing in mind this was around 3 hours later) dsd asked "are you driving? Just I saw you had a drink" tbh I didn't think much about it as I'm so used to these sorts of comments all the time but my sister was appalled and completely embarrassed in front of everyone, I do remember the room went quiet and I laughed it off by saying something like, are you the police?? DH said nothing
Anyway since my sister has pointed this out I do wonder if she should be called out on listening to grown up conversations and passing what feels very much like judgement?