Bloody hell there's some really appalling ignorant, judgmental even disablist posts (and against disabled children!) on this thread - disgusting!
It's NOT just Sen - which are often undx at this age anyway - there's any number of other conditions which could be complicating matters.
My dd was a late toilet trainer, not dry in day until 4 and not dry at night until about 6, I later learned likely due to her then undx physical disability.
I worried at the time and even queried with dr and HV (who with hindsight I'm pissed off they didn't put this together with other symptoms to Dx the disability - whole other thread!)
So as a non hcp (and clearly even the hcps get it wrong) you cannot possibly know there's not a medical reason.
Support your friend, perhaps discuss with her IF she clearly asks, what she's tried so far and what the outcomes were - which could be revealing of a potential medical issue - and encourage her to seek help from hcps if it seems necessary.
But stop with the assumptions that there isn't a reason beyond her and her child's control.
You're not I don't think a medical expert yourself?
"whereas to me the size of her DD says she is far too developed for nappies." Physical size has NOTHING to do with maturity, brain development etc I don't know where you're getting that idea from?
Language acquisition and other unrelated skills ALSO has NOTHING To do with it, my dd was talking in sentences and even multisyllabic words from 2, counting up to 20, excellent climber (again quite possibly due to her condition) - none of which meant the issue affecting toilet training didn't exist!
My dd is very tall and always has been BECAUSE of her condition, she was in age 6 trousers at age 4 for the length, I had to alter the waists as she's also very slim, there are many Sen conditions where being tall/big is also a symptom. In fact I'm wondering if your friends child's appearance IS symptomatic in some way.
You sound very judgmental while also being very ignorant medically.
Frankly if what you're saying about the nursery is accurate they too should know better!
"Just tell her. If there’s no SN there’s no reason" gah! AGAIN many children are still undx for Sen AND other medical conditions at this age, it's incredibly hard even getting assessed let alone a dx!
And AGAIN it's NOT JUST SEN that can make it difficult.
Dd FINALLY was dx with her GENETIC physical disability, which I now know from learning about the condition myself (and I'm still learning not least because so are the experts in it!) she ALSO had CLEAR physical appearance markers and symptoms AT BIRTH, when she was...12!!!
And THAT was a combination of me losing the plot with her suffering symptoms and needing time off school as a result AND us being LUCKY to meet with a locum GP with an interest in the medical specialism it fell under and giving us the referral I'd been asking for for years!
I've no personal experience with Sen but from friends with dc with Sen and also reading here and elsewhere I'm aware it can be an absolute bloody nightmare getting even a referral let alone a dx for those too.
Hell I've read on here of ADULTS in their 20's/30's/40's getting dx with Sen, I've a friend who wasn't dx with aspergers until her 40's, another who was dx with dyslexia and dyspraxia in her 30's.
So unqualified and inexperienced people claiming online that this child clearly has no medical issues is beyond ridiculous!