Vastra has travelled now. Do you think that qualifies her as a companion? In Simeons office she is definitely filling the role.
Well, Vastra, Jenny and Strax all travelled in the TARDIS in AGMGTW, although we didn't actually see it.
I suppose it depends on how you define a companion. My definition (not necessarily the official one) is that they have to fulfil one of two criteria:
a) They travel randomly in the TARDIS, as opposed to being given a lift (that would make a very long list - including Nixon, for instance).
b) They help and support the Doctor over numerous stories (eg the UNIT regulars).
By that definition, Vastra doesn't quite fulfil either category, though hopefully she'll eventually clock up enough appearances to fulfil b) at least.
Then again, it's not an exact science. For instance, I'd count Sara Kingdom as a companion, because she travelled a lot, even though she was only in one story, but so did Kazran and Abigail, but I wouldn't count them as companions. And what about Nefertiti?
