Thanks for all the good wishes, everyone! Your help has meant a lot through all of this. <3
It's a hard situation now, as Delilah (Dotty's sister) hates my new rat Arya and intros have been the worst I've ever had, but my other two rats are terminally ill and showing their age, so at some point Delilah's going to be alone for a little while before I can get her used to Arya, I think. ):