crystalwings, I feel your pain! We have issues with our 2yo's sleeping habbits too. He has coslept since birth and when we moved just before he turned 2, we tried our hardest to get him into his own bed. He would wake often too, if we didn't sleep with him. The difference being DS will sleep with DH. So now with me being 33wks pg with #3, DH and I sleep withhim in a double bed in his room again because it's just way too hard for me to get up 2-4 times a night and sit with DS until he goes back to sleep. So one of us gets a reasonable nights sleep, then the next night we swap. But DH is going to be starting afternoon/night shifts with work again soon, so I have no idea how I will handle it. DH will take charge of the bigger two when he's home, but there will be nights when it's just me, so it will be interesting. I am just oging to go with the flow.
I plan on cosleeping with #3 and that is going to be more important than sleeping with DS because I will be bfing. When I had DS, DD wasn't the best sleeper either, no actually she was dreadful, so I was up ALOT in the first year or so of his life, dealing with non sleeping monsters, just praying for more than 2hrs sleep.(Sorry don't want to scare you, lol!) We ended up putting a double bed mattress on the floor of our bedroom and DD slept there with DH(when he was home) and I slept in our bed with DS so I could bf and settle him through the night easily. It was the best way for me to maximise sleep. DD was ok if she could hear me and DS, I wcould tend to both her and DS if they needed me and it was just reassuring for me to have them both with me on the nights DH wasn't home. But now DD is 3 1/2 she sleeps through most nights, and has done so for about a year (slept most nights, ie 4out of 7 she will sleep through. Now it has gotten better and better and she will sleep through 13 out of 14nights). I'm just praying that as DS gets older he will figure out sleep is good and he doesn't need DH or me next to him.
Maybe you could try to start getting your DH to do things with you to prepare for bed time. Just start slowly with him maybe sitting on a chair in the room or something, then he could sit next to you with your DD on the bed, then he could read her a story...ect. It definately makes life easier when you can let your other half do things if you're busy with bub.
Oh and BTW, I didn't find cosleeping with both kids difficult. DD would sleep through DS screaming alot of the time, and vice versa. Bu tusually because I coslept, DS wouldn't really have a chance to cry because I had my boob in his gob before he managed to utter a noise! Sometimes they woke each other, but generally they were easy to get back to bed and I can only remember once or twice when I had them both up for more than 30mins having a party together and usually me crying on the bed, lol. The biggest problem I had was them waking each other in the mornings, but it didn't bother me so much because I had one awake anyway, so to have them both up wans't a big deal, iykwim.
I do agree with Marcellus, that her ears might be an issue for her sleeping. My DD had terrible glue ear and when we eliminated dairy from her diet as suggested by the paed ENT, she slept ALOT better. He r glue ear got better and we didn't need grommets or any more antibiotics after her having about 6 courses!