We also co-sleep. Our daughter is 20 months and we have also had some bedtime struggles, but we are not yet ready to transition her out of our bed. I say this to let you know that I have no direct experience to offer you. However, I bet if you got a hold of the No Cry Toddler Sleep Solution (or something like that) by Elizabeth Pantley, you would find some good ideas. She also wrote the No Cry Sleep Solution, which I found helpful at one point. I think both books would have advice for you about transitioning her out of your bed. I also really recommend reading the collected comments on the Berkeley Parents Network on transitioning -- you can find it on line if you google 'co-sleep transition'. Great collected wisdom of a community with a lot of co-sleepers.
Some things that have helped prevent my daughter from getting riled up around bedtime, or defused it (to a point) whene she does are: having a nice, long bedtime routine that starts well in advance of bedtime (when we shorten it by skipping the bath, we are more likely to have trouble), talking to her throughout the routine about what is going to happen next, keeping the routine confined to the bedroom, and being as mellow and relaxed as possible ourselves.
I read somewhere that one thing to do is to bore your kids to sleep. This has sometimes worked -- if she just isn't ready to lie down, I lie down myself and let her bounce around the room herself for a while. She tries to engage me in conversation or activity but I just tell her that I'm tired and resting and to come lie down. Often after 10 minutes of this, she gets into the bed of her own accord and settles in. I do think that getting scold-y and stern turns the whole thing into a power struggle -- although I have definitely gone there myself and it is so hard to avoid when you are in the thick of things.
Finally, as with all things, it will change with time -- at least, that is what I have found again and again. Remembering this has helped me stay calm and patient.
Hope this helps and congratulations on your pregnancy!