Covid isolation question...sorry

[Notonthenewrug]

I'm finding it hard to get a clear answer.

My DSD's mum has tested positive for Covid. DSD currently neg. We are meant to be collecting her tomorrow for a family Xmas get together - 17 people.
I can't work out if she is supposed to isolate as she's in the household of a positive case, or expempt as she's 12?
Either way I think bring her to a get together of 17 people is a bad idea?
Anyone know the rules? We are in Wales.

She doesn't have to isolate because of her age was my understanding after reading the new guidelines from the Welsh government website. Imagine how she's going to feel if she's testing negative and you don't include her. Yes the rules are ridiculous but she's going to feel terrible if you leave her out at Christmas.

gov.wales/self-isolation#section-83763

No isolation but 7 days LFT to be taken and logged. Other than that you have to risk asses your exposure.

@Seb342 absolutely. However I have several family members who tested positive, the household members were initially neg but later tested positive. Im not bothered about me but they are having a family party and exposing 17 other people.