[Solved] Going to the attic whilst mummy has sex

I had an interesting conversation with my 5 year old daughter this evening.

When I was tucking her into bed, she started telling me that her mum and her mum's partner tell my daughter and his 5 year old son to go up to the attic and stay there. She then said that there's toys in the attic, but said she doesn't like going up there because mum's partner's son's scary halloween costumes are up there. She said she goes to her room and lies on her bed instead. She said she's not allowed to go anywhere else,

I asked what mummy and her partner did whilst they were up in the attic by themselves, I asked if they did this when they needed to cook dinner or something like that. She told me no, they get sent up there when mummy and partner are having [censored].

I was surprised that she knew the word [censored]. She then said 'Mummy said I musn't spy on [censored]'. I asked her what she meant. It turns out that she had gone to see what mummy and partner were up to a couple of times and caught them at it. She was told to leave the bedroom, and my daughter told me they then carried on 'for a long time', both times.

She was very confused about what [censored] is, and I tried my best to tell her on a 5 year old's level. Personally, I feel she is far too young for too much detail and I just said it's something grown ups do when they want to show that they love each other.

I also felt I should say, and I did it in the gentlest way possible without trying to make anyone sound bad, that my opinion was that if children are awake and in the house, parent's should be looking after them, and [censored] was something grown ups should do at a time when there aren't children about.

I told her that she hadn't been naughty (as she seemed a bit worried about 'spying' on mummy and partner), but that if she knows it's happening next time (it seems she's clued up on when it's happening now), to not enter the room (I don't want her seeing anything inappropriate).

Her mum is [censored] obsessed and has been highly promiscuous in the past. So, I knew where the conversation was heading, as it was only a matter of time. She often comes to the door adjusting her knickers, hair in a mess, red lips...

I was wondering if anyone would have dealt with this differently? And what people think in general. We've all heard our parents having [censored], but this seems more of a cause of concern to me.

Also, although it sounds like they are using the attic as a playroom, and apparently it has stairs up to it, how safe is it? My daughter says the floorboards creek. She also has asthma, When I was little, our first house had an attic but I used to get told off from going in there as it was too dangerous.

There's a lot more I could say on the [censored] thing and my ex's sexual behaviour, but I could end up writing a whole essay!