Getting worried....UPDATED

I'm 6 months pregnant and I'm worried that my now youngest (1yo) will be the death of me when this baby gets here.

It's 1:50am and I've just had to calm her down and put her in the pack n play in my room so she'd go back to sleep.

She cries when I try to lay her back down in her bed in the room she shares with her older sister (2yo) so I just put her in here with me.

When the new baby gets here, she will be in that pack n play...

Any advice?

UPDATED POST ADDITION: The obvious is to just put her back down in the room she's in. But my concern is waking up my other baby. Then I would have 2 crying babies in the middle of the night. YES, this happens but not all the time.

Seeking advice from parents who have children who shared a room at an early age while expecting a new child and/or while you shared a room with the newest addition. What problems did your face? How would you go "fixing" this?