Thanks for the info!
You say you have tried the EASY routine, do you want to set one up again? That's what we would try to do with you, it might not be what you want
but from what I can see here, she's not getting enough day time sleep and she is waking up at night because she's overtired.
Average A times for 6 mos are between 2hr30-3 hours, some babies get less, some more, and that's from eyes open to eyes shut. And 6 mos is the usual time for babies to drop their third (shortest) nap, the last nap of the day, the cat nap. So I would probably suggest trying to get Poppy on to a 2 nap routine and hope that would help her nights.
Have a look here for some sample routines, but bear in mind that each baby is different, so maybe none of these would fit exactly.
Sample EASY Routines from 0 - 13mths+Lastly, I have to say again if she has on-going digestive issues, I'm afraid no amount of tweaking and routine planning is going to help her sleep.
HTH.