L.K.
My daughter went through the exact same thing...and we did the same thing too; we'd let her crawl in bed with us and just stay there because we both work and who wants to fight over going back to bed at 2 or 3 in the morning?
What I did do that worked at least some of the time is I told her that sleep helps her grow but it only works if she sleeps in her own bed. Not sure about yours but my daughter is obsessed with wanting to grow and be big and strong so she was more inclined to stay in her bed... there are still nights (now at 4 years old) that we get our little visiter in the middle of the night but it's no longer daily and I enjoy cuddling with her at night and know that in another few years I'll be wishing for the days she wanted to snuggle at night so I don't get upset. As far as the new baby coming I'm sure that will cause a bit of a set back because your daughter will be wanting to do whatever she can to spend time with you and demand your attention but hopefully you can get her out of the habit before the baby's born... Best of luck and enjoy it while you can!!