My little darling (20mo) has also had problems with sleep, as we also rocked him to sleep, then carefully decanted him into bed, etc. However, the Baby Whisperer is very sensible and humane about withdrawing your support, in such a way that you (feeling hormonal as you are) won't feel like you are murdering the poor LO. After all, BW, points out, we have conditioned our LOs to certain expectations, and it's not kind to suddenly abandon them (the expectations, not the child).
However, I must note that there has been an element of controlled crying in the way things have developed with DS, as sometimes he starts up at 5:30, which is really too early. The BW does counsel leaving a child for a bit to settle, but to be honest, sometimes I am so tired that the "a bit" is "a bit" more like CC! However, I have only done this after he did demonstrate he could settle himself, so my conscience is almost clear.
Sitting in a comfortable chair and singing/reciting a story/ repeating "sleepytime" while the little one is in bed complaining was another part of the new routine which also worked for me.
By the way, it is interesting that DH and MIL still almost rock DS to sleep, but DS knows what to expect from me, and lie down (even if not asleep) happily when I do it. It took a lot of patience, though!
Just a thought: as a preparation for the arrival of the new baby, maybe you could start a new practice of reading a bedtime story in the near-dark, AFTER DD is in bed, after milk and everything else. It will be your special time, which she has with you thanks to the new baby's arrival. You can also record your reading books, so she can play them for herself at other times.
Good luck with the sleep, and also with the new baby!