I guess I could move Celeste to another room while they have out-of-cage time.
However, I think Stella didn't want to get out of the cage yesterday because I was in the room, as she is terrified of humans (and maybe because she didn't know the room) but I can't leave them there unsupervised.
Maybe I am overthinking it, but would it make sense to try to tame her?
I could have some taming sessions in the budgie safe room until she gets to the point that she can jump on my hand to eat seeds. After all, she is not even one year and a half old (so not too old to be tamed), and Sid already steps up on my finger to get a treat (even if he bites me after that, I talked about it in my other thread "Celeste's training journal") and she might copy him as budgies are known to do.
Doing the taming sessions in the budgie safe room would also make her get used to stay there.
Or would it better to keep things as they are? Perhaps she might decide to follow Sid out of the cage anyway.
@iHeartPieds, that is a good idea, thank you, after all almost a year has passed since Sid and Stella had their first and last visit to the vet, so taking them there would be the right thing to do regardless of Stella's current condition.