Hey, she's not completely awful.
She showed basic human decency by being appalled with the treatment of the Ood.
And she saved Donna and Wilfred from being killed by a falling Titanic.

And, uh... oh, she told the Cult of Skaro they weren't making anyone the designated redshirt.

... see, three examples over thirty-six episodes and an X-mas special! Not totally awful.

Now, selfish, on the other hand...