2 hour night wakings - Please help to stop these!

[Shylily]

DD 8months has never been a very consistent sleeper. There are lots of contributing factors (jet lag at one point, illness, teething, bad habits on our part) but she's now developed the habit of waking fully for at least 2 hours if she wakes at night.
I have tried just about everything.
First I just put the dummy back in, then if she continues, try feeding (FF), if that's not the issue, she usually wants to be picked up and will scream bloody murder if she's not.
She will not sleep in our bed, so I can't even do co-sleeping to get some kip.
Eventually, last night I left her. I went back every 5 minutes until she conked out after 55 minutes of crying.
Tonight she's been going for over an hour (with me popping in to pat or put in the dummy).
I have given teething gel, calprofen, tried water, formula (doesn't want food or water). She will stop the instant I pick her up but then wants to sit up and chat. I know from experience that she will do that for a full waking cycle which is at least 2 hours.
I don't know what to do now. I am exhausted.
I tried 'contolled crying' with my DS2.4 when he was about 9 months old after a blip with his sleeping but the longest crying spell was 3 minutes! I didn't really advocate the method and there's no way I would have done it with him for any longer, but then again, I didn't have to! I am just desperate to break this cycle and let us all get some sleep.
I have got her day naps under control and for the first few nights of doing a recommended day routine she slept through. No longer.
Can anyone help?!
I have to go to her now as she's in such a frenzy, I don't feel I can leave her any longer.

How long has this been going on for? DD (6 months) did this last week but it only lasted for 3 nights. Just a blip?

It's been on and off for months now. She had 3 nights sleeping through about 3 weeks ago, otherwise, it's been about 6 weeks!
She wasn't well for a week, and before that she cut a tooth. She stops crying the moment I pick her up and starts as I put her back in to bed. If I sit her on my bed (even in the dark) she's fine but if it even looks like I'm trying to get her back to sleep, she starts crying again.
She's also just developed separation anxiety in the day. I can't leave the room without her becoming very upset, but this does not affect her day sleeps, she squawks once then goes to sleep.
I started a similar thread about 3 weeks ago, but I can't find it!

Have you tried the retreat method with her? You sit with her til she goes back to sleep, but don't interact at all other than to occassionally say 'shh go to sleep'. But over a few nights you move further away from the cot til your out of the room (your supposed to stay in one place for 3 days then move).

We did it with our DD and it did work, but took a long time, about a month, but that was more to do with us than the method, which is supposed to take a week to 10 days.

Also, I would refuse to give milk and just offer water and certainly try not to talk and chat with her, just keep it all quiet and dark.

Hope it stops soon for you