[quote=Kaga]
I don't really see the Mary Sue aspect. It's not like she doesn't have her own problems to deal with.
[/quote]

You mean aside from the fact that the episodes she did appear in went out of their way to show how awesome she was? And the whole "married to the Doctor" thing, which is kind of the classic fangirl wet dream? Or the fact that she's conveniently a Time Lord due to some contrived Deus Ex Machina bollocks?

Edit: I'm typing on a Kindle. There's going to be autocorrect problems.