Thank you so much, Sandra, Pat, MA, Beth, Lei, and Sam!
Thank you for your advice, MA, Pat, and Beth! I will certainly put these excellent tips into practice immediately! Answering your question ,MA, of how Sierra is doing aside from the intro, she is great! Acting quite herself, even more lovable when we're alone, in fact. She's been eating great, and has thrown up only once all week. We're still having our fun playtime and snuggle time, and she still has her beautiful sparkle in her eyes.
Now if she will just tolerate her new little sister! Also, yes, they will definitely have separate kennels for the journey home.