Theory:Doctor Who television discontinuity and plot holes/The Doctor's Wife

Why was this episode titled, "The Doctor's Wife" ?

It was pretty clearly established that the TARDIS has had unrequited feelings for the Doctor for centuries. The Doctor wasn't fully aware of those feelings even though he returned some affection, in the way that someone has affection for an old trusty possession. Once the Doctor was made aware of the TARDIS' feelings for him, he began to understand and reciprocate those feelings. The term "Doctor's Wife" refers to the fact that the TARDIS and the Doctor have always been together, developing a deep bond, linking them as partners throughout time and space.