"I’m not sure actively trying reconciliation is going to help because however you do it, it can feel like you’re on his side (I know that’s not the case at all - my experience of you is wanting the best for them both.."
Thank you for saying that, I do really want the best for them both, it has been very hard balancing both their needs.
" I wonder if spending time with her in her own might help?"
I do as much as I can.
"...my theory is that if she’s reassured of her relationship with you, it’ll free her up to use you as a secure base from which to revisit her relationship with him?"
She is very anxious and insecure, she does seem to doubt my love.
"I also wonder if involving her in his care, reinforcing her place as the older sister might help?" We do try that as much as we can.
"It’s a different situation but I’ve found that reassuring my DD of how much I love her, noticing the positives, recognising when she does something caring etc has massively helped her relationship with her brother in a way that all the refereeing in the world hasn’t."
Any tips on how you have done this, jellycatspyjamas?
"I think sometimes the only way with teens is going right back to basics, because research shows that developmentally their going through the same type of brain development as toddlers. So, think toddler in big body rather than adult in little body, if that makes sense?"
That's a very good point. However, they are toddlers with potty mouths, who swear and are generally much ruder and more unpleasant than normal toddlers. I do find it easier to be loving to my 8 year old because he responds well. My dd is more likely to be rude to me.