OP I think you are probably referring to the AQ50 test which I mentioned, and if so it is only a screening tool. Her score does seem lower than cut-off BUT it can be hard to answer accurately, let alone for someone else....
A lot of what you have referred to certainly do very much seem like autistic traits..... one autistic trait is spotting patterns, including behavioural, and that is probably why so many people have picked up on things here immediately.
So you have:
Friendship/social struggles
Sleep issues
Anxiety
Plus all of these sounds very autistic to me:
"Things she has traits for is - clothing - just this morning changed her school T-shirt for another as it was 'itchy'.
Takes her at least 5mins sometimes 10 to put shoes on as she pulls them so bloody tight 🙈
Loves to draw but it's usually the same thing over and over
Likes to watch certain TV shows over and over too - I've managed to get her to watch something different over Xmas on iPlayer.
Bites her nails to death!
I noticed one trait was hair twiddling - I do this occasionally when bored lol!"
So there you also have sensory issues and also evidence of "restricted and repetitive behaviours", in addition to the social struggles a school and all of your other (significant) concerns around sleep etc.
Worth having a look at the actual diagnostic criteria, which are based around social and communication struggles and restricted and repetitive behaviours. As all of the screening tools etc. are really only looking at traits of these, which obviously can vary from person to person. A lot of what you have said does sound in keeping with the diagnostic criteria, although obviously only a professional can assess this through a combination of parent interviews, ADOS test etc.
I really think it is at least worth having a chat about this with her paediatrician..... as an autistic mum of at least one autistic child, everything you are saying fits. I'm not saying there is no other possible explanation, just that I really feel based on direct personal experience that it is worth exploring further.....
"Mild autism" isn't really a thing...someone is autistic or not, but some autistic people are higher masking than others and so other people may notice their autistic traits to a greater or lesser extent..... unfortunately though, high masking can often be devastating for mental health and wellbeing, leading in the long run to coping much less well, burnout etc.....people can often appear to cope well until they really don't...... the reason that "levels" of autism are not really given in the UK now is that how someone is affected is so dependent on the particular circumstances, sensory inputs, stresses they are under etc.... it isn't as simple as someone being slightly autistic or more autistic, and the degree to which it is expressed can very much depend on all manner of other factors.... hope I am explaining this ok!