Oh dear it's so hard when you can't get the sleep you need yourself, isn't it! I'm sorry I just noticed you posted on general sleep yesterday too but haven't had replies yet - probably best to keep to one thread at a time if it's about the same issue, would you rather continue on here (we may be able to copy and paste your post on general sleep here so it's all in the same place) or start afresh over there?
I'm not sure what the nights are usually like as in your other post you're still talking about just the two NWs - is that still mostly the case, but you have the odd horrible night thrown in? Tbh I suspect you'll have to hang onto that night feed a little longer, most LOs I think will still be having one at this age, and there's usually a growth spurt around 6mo too. Has she started solids at all? I just ask because often their tummies can be a bit sensitive when they first start, which can cause sleep disturbances and you may need to go quite slowly with that if she is uncomfortable. Of course teething is possible too, I think 6mo is average for those first teeth - do you think that might be going on too? I just ask because it seemed like things were fairly stable, albeit with a nf you didn't really want and cuddles in the early hours, which tbh isn't so unusual. But then things suddenly seemed to change for the worse, with lots of crying - I'd guess some sort of discomfort, or could be OT too if her daytime sleep has decreased over this time, or her total wake time increased? If you think routine issues are more likely, would you mind posting what happened on a real day, eg yesterday/today, rather than an average routine? Might help us to get a better idea of what might be going on... (((Hugs))) it's frustrating and tiring, especially with an older one to look after too - so I struggle to imagine having older twins!