Thanks, Heidi and Elyse! Galaxy is coming along more quickly than I'd thought she might. I shut the end opening of the carrier, and I put some treats in it and then lifted her up into the top opening. That went quite smoothly, and she settled down to eat her treats, then dashed out. So that's going quite well!

She and Sparkler are co-existing, not buddy-buddy but not openly hostile toward each other. I make it a point to give them both plenty of affection.