I know how you feel, my DS was like this and it was hard enough having just him let alone an older DD! I'm gonna say reflux too, that's what DS had and after a week on medicine he was great! I found that bouncing DS on my knee really helped and being on his tummy upright on me too. If your bub does this I think that she likely has silent reflux! Have you got a bouncer? That's useful to getting them off to sleep, the bouncing somehow helps with the burning if that makes sense? We let DS sleep in our pram during the day because he could sleep upright, he loved it!

With the dummy, maybe try offering the dummy straight from boob when she's sleepy (when she's done feeding obviously) - she might be less likely to notice the difference in it and gradually get used to it enough to take it when she's awake?

I really, really hope you get some sleep soon. You are doing a fantastic job, take some deep breaths and remind yourself!