Well, I always did find them a little similar in appearance when I was younger, cause Toph is pale, brunette, thin and has faded blue eyes. They look alike here because you went for realistic and gave her lips rather than mouth lines. Every art I see that someone gives Toph normal lips while keeping an anime style like yours, she ends up looking like Diva to me.
It's disturbing because I then start imagining Toph going giggling psycho like that crazy bitch, or said crazy bitch with Toph's Earthbending. Neither scenario ends well for mankind in general. Blame my horror-filled otaku brain.
With that being said, your art is awesome!