Thanks for the replies everyone. Phoebe is around two years old - she was a rescue dog so the vet isn't sure. I did have her in the crate at first but she is a very well behaved girl - no accidents, no chewing, ignores the cats (when they let her!) - so now she only goes into it if she wants to. I'm probably being silly worrying about her so much and hopefully we'll both feel better as we get used to each other.