Absolute despair over 6 year old bedtimes, please help

[opalescent]

Dd is 6 nearly 7. No additional needs or health conditions.
Really, really struggles to fall asleep at night. Always has to some extent, but it is dreadful at the moment.
Bedtime routine is:
Into bed at 8pm. Reads with Dad.
Settling down to read by herself with a lamp at 8.30. Quiet and gentle music on the Alexa.

From this point, it is anywhere from 10.30 till midnight (at the absolute worst).
We have tried:
Rapid return
Going up every 5 minutes to reassure
Moshi app
Lying with her

Nothing has consistently worked. I have zero evening because she loudly reads or chatters to herself, and regularly calls for us. I am actually read for bed myself before she is asleep most nights.
She is not naughty, and stays in bed, but cannot fall asleep. She generally seems fine during the day/ at school, unless it's been exceptionally late.
I would be happy to accept that maybe she doesn't need much sleep, except that she looks totally exhausted by 10pm, glassy eyed, and clearly fighting it.
I would be happy to lie with her, if it consistently worked, but it doesn't!!!

Once she is asleep she sleeps soundly.

Please help 😩

Id do bedtime earlier, so into bed and reading for 30 mins at 7. Then at 7:30 you go in lights off and let her have an audiobook, a decent lengthy several hours long one not a kiddy 5 mins one.

I would introduce a sticker chart with a reward after 5 days for staying in bed every evening for a week, then repeat each week for a month until it becomes natural.

When are you turning off the lamp/ no more reading?

My DS is the same age, always been a night owl. He goes to bed around 8.15-8.30, we read him 3 chapters of a book, then it's lights out. I generally sit with him for 10-15 minutes just chatting, hugging. When our dinner's ready, I go to eat that and leave him to sleep. He generally is out by 9-9.15pm and up for school at 7-7.30am. He seems to do fine on this amount of sleep.

I wonder if leaving the light on isn't helping?

I have a night owl. Some battles aren’t worth fighting. DD could no sooner sleep at 7pm than I could.

(both recently diagnosed with ADHD)