I had some similar "how will I manage pregnancy/new baby with my toddler" questions too, but before I figured out any satisfactory answers, I got pregnant. So, it's a work in progress! I'm going with the idea that I've got another 7.5 months to make some changes with my son (who is currently 17.5 months old) and that after the baby is born...well, it'll be an adjustment for all of us. I'm currently caught up in trying to figure out how nap time with two kids works, especially when you factor in different nap times and room sharing.
If long-term co-sleeping isn't a mandatory thing in your parenting philosophy, you'll have plenty of time to start peacefully transitioning your daughter to a new sleeping arrangement. "Big girl bed" in her own room or a floor bed next to your own, however you choose to word/manage it, it doesn't need to be a traumatic thing since you'd have months and months to do it gradually. My son is currently in a crib, but he's going to need to transition to a regular bed at some point. I'll have the baby in bed with me or in the co-sleeper for a good 6 months after s/he is born, but I think I'm going to start transitioning my son a month or so before the baby arrives anyway.
My son stopped nursing to sleep a while ago, but we do have a bedtime ritual that will need to evolve over the coming months as I get bigger. He's in a stage of total mommy-itis, and only wants me for bedtime, so that's one thing that will need to change. I'm holding onto our routine (rocking, sipping milk, singing, then into bed) for another few weeks because it's such a special time, but I know I'm just not going to be able to keep him on my lap comfortably in another few months, nor am I going to be able to pick him up and lean over his crib. I don't really have a new plan, but I feel like I'll figure it out as I progress and see how he reacts. Perhaps you could first work on transitioning her to her own bed, then move on to changing your bedtime routine.
If she's already 19 months and down to just 3x a day and you're not pregnant right now anyway, the bf thing might work itself out on its own. I've read lots of moms talk about how their older toddlers weaned themselves as the pregnancy progressed because they didn't like the way the milk tasted.
Whenever I feel myself start to worry about the logistics of two little ones, I remind myself how many parents before me have done it under more difficult circumstances! I remind myself that my son will be fine, and that he'll be ready for a new phase in toddler hood anyway by the time the baby gets here, and what a wonderful older brother he'll make. I remind myself that he won't suffer any lack of affection or attention...it'll just be a new routine for all of is. Life is all about change, right?