DSD is 15 in a couple of months.
She is tall (about 5 foot 8) size 8 feet and a little overweight.
She is otherwise healthy, eats like a horse, no sign of spots/acne or greasy skin, her figure is not "developed" - no sign of much of a waist or boobs (but this may be as she is on the plumper side).
Her sister (2 years older) started at 12.5.
She is rather immature, fundamentally and behaves rather more like an 8/9 year old.
My DH is trying to get his exW to see that there might be a problem. She seems to say that as some girls dont start til 16/17 (according to the internet) there is no problem- in my understanding those girls are likely to be trained athletes, underweight or anorexic or have a family history of late menarche.
Any experiences would be helpful. I and all my mates started between 12-13 which seems to be the norm, still. As far as we are aware all her friends have. We have spoken to her about it and she is not bothered at all, understandably.