Wow, sounds like you're having a tough time atm. I think the longer you wait to change things, the closer it'll be to the arrival of #2 and DD might relate the two and feel resentful iykwim.

Do you want gentle parenting advice? Are you wanting to change where she sleeps, how she gets to sleep, do you want to stop camping out? Whatever you do, it'll take time, commitment and patience on your part. I'd recommend taking a look at the raising children network stuff though.

Everyone is different and I'm not 100% sure if you want advice like this or not, but if it was me, this is what I'd try. Establish or continue her bed/nap time routine. Tell her it's sleep time and put her to bed. Lie down with her like you're doing. The next step is to gradually move away, little by little over a week or two. Start with doing what you're doing but move away a few more inches when she gets really drowsy. Then you can start lying further away and start moving away when she's a little bit less sleepy. Gradually you can lie at the door when it's nap time and hopefully in a few weeks you'll be able to put her down and go! Oooh, it sounds so simple, doesn't it?! If only!

Does she have a cot or are you happy having her sleep on a mattress on the floor? When she screams out at you, is she crying and upset, or just loud and annoying iykwim? Can you ignore the calling out, tell her before you put her down that Mummy won't come if she yells out (but Mummy will come if she's upset) and that if she can't sleep she still has to lie in her bed and rest? What does she do when you go in? Do you resettle her and can you leave again? I know she's only little, but you might be surprised at what she'll understand over time.

I hope you find the solution you're looking for. GL