Keep on reassuring her. I am glad you are willing to cuddle and rock her; she is still really a baby and it's not spoiling her to do this. Some kids really need their routines, and her dad's trip, even for just two nights, rocked her little world, even though you followed the same routine as dad; in time, she will be fine with either of you doing it, but she was very attuned to his being there at bedtime. Don't change her schedule -- stick to the one you were using before this.
The trembling and vomiting at bedtime are a bit much, but some children do tend to vomit when very upset, and this seems so clearly tied to bedtime anxiety. Now that your husband is back, has he returned to putting her to bed or are you still doing it? If you are doing it, you could try having him return to bedtime duty exactly as he did before. But you might also stay in sight where she can know you too are around.
Remember, she is at an age where she may still think that when one of you is gone -- especially at bedtime -- you are gone for good. Out of sight equals disappeared forever, to a small child. She is right on the cusp of being old enough to transition to knowing you are really there when she can't see you, but again, at bedime many young kids suddenly seem much younger, needier and clingier than they are during the day, when they can seem confident and outgoing. That is very typical for toddlers at bedtime.
I think you are handling this well, truly. Keep to the routines, make sure dad is putting her to bed, but also be where she knows YOU have not left, and continue being gentle and never fussing when she vomits. She is not old enough yet to "do it on purpose to manipulate you" as some moms on here sometimes claim little kids do; she's just not old enough yet to pull that kind of stunt. She's vomiting out of pure stress.
It's only been three nights of this; you may have to let tiime take care of it, and the fact that dad is back.