Having to move step daughters room downstairs

Lacey
We have three bedrooms upstairs in out house, this includes the master. My son (6) and my step daughter (8), (she lives in a different state and is only here in the summer and some holidays) have the other two rooms upstairs. 
We are wanting to put our new bundle of joy in the room closest to our room which is my sons room, move him into my step daughters room (he has severe anxiety and needs to be close to us) and then move my step daughter downstairs. This will not go over smooth at all. 
What ideas do you guys have to make this easier for her to be down stairs?