How best to support AuDHD child with sleep anxiety/insomnia

[Changingnameagain]

Our DD age 7.5 hits rocky periods with her sleep every 3 months or so. We are in one now and I am exhausted and also ill as a result of not getting sleep myself.
I need ideas on how to handle better/differently.
We've resorted in last few days to giving Piriton. This worked well on night 1. It didnt work to get her down to sleep last night. In the end I just told her to bring her chair bed into our room and sleep there. I was too ill to keep trying ti get her down in her own bed. We were 2 hours in and DH was out and had been since mid morning.
Ultimately though I just dont sleep well with her in the room. I am AuDHD and have my own issues with sleep. Once it is disturbed or if I perceive there's a risk it'll be disturbed then it can take me anything up to 2 hours to get back to sleep as my body goes into hyper alert / hyper vigilant state. So despite white noise playing and ear plugs I still hear any small rustle she makes in her duvet etc.
Friends gave said we should order melatonin online. Im reluctant because I've read it can prevent body making its own naturally, can hinder puberty and also cause night terrors. I dont want her dependent on meds to get to sleep. Equally we cant keep spending 2-2.5 hours a night to get her down to sleep. Or keep functioning in demanding jobs when she's woken us up multiple times in the night to tell us she's awake and cant sleep.
She was a decent enough sleeper as a baby/toddler. Her anxiety is just off the wall about sleep.
She has a good bedtime routine.
No screens from 6.15.
Takes magnesium supplement at 6.20 ish before bath time.
Has quiet time in room with audio book or reading and coloring until 7 45pm. Then we go up to put her to bed.
She will then be coming downstairs every 20 mins from that point. She either says she doesnt want to sleep cos she's scared of a bad dream or she wants to sleep but her brain wont switch off.
She said the other night a line from a song she's learning with school choir just kept looping in her mind and she couldn't turn it off.
In the week we need her up at 6.30am so we can get to school/work.
Any suggestions that arent meds? I'm so sad for her she is so anxious about sleep. And I'm also on verge of my own mental health going down toilet due to sleep deprivation.

Is hypnotherapy for kids a thing?!

How much exercise is DD getting during the day?

Some people find a 2 way monitor, dream pad pillow, weighted blanket, human sized teddy, brushing, meditation, tents, various lighting, worry book, doodle book/pillowcase helpful. Some find the elastic band technique works. Or an adapted version of gradual retreat.

Is DD on ADHD medication?

Although I wouldn’t also consider medication (there are other options if you don’t want to try melatonin) for the difficult periods. Melatonin is generally considered one of the safer medications, and sleep deprivation and stress have their own consequences.

My AuDHD DD has been on melatonin for 5 years now (ages 7 to 12 - she's coming off it gradually now) and the paediatrician hasn't raised any concerns about it.

She was a nightmare before! The song on a loop thing sounds very familiar.

100% get a referral for melatonin. In a lot of countries its over the counter!