Board Thread:The Panopticon/@comment-9435571-20140927221308/@comment-1432718-20141101041522

Katarina was intended by the production team to be a companion.

As for trips in the TARDIS, Katarina has had more than one trip. There's at least one short story adventure in which Katarina participates. Therefore, she's not really a valid comparison to Courtney. Anyway, as both CzechOut and Skittles the Hog state above, travelling in the TARDIS is not what defines a companion on this wiki.