She's not human.
Let's look at her face, shall we.
You see that face. It's the same face you always see on her. That "I just ate a lemon and I am confused by everything" face.
The only logical reason for her to have this face on at ALL times is if she has, in fact, always just eaten a lemon and is, in fact, confused by everything. You see, lemon juice is an acid. A person cannot consume so much acid without causing a serious imbalance in the digestive system. That is, of course, unless her body chemistry is much more acidic than a human body. You see, blood is basic. Not that it's a simple thing, but it is a base, and bases neutralize acids. As such, Miss Zellweger must consume additional acids to counteract the bases pumping through her system. Still, a human does not find his body's blood neutralizing all of his acids.
Why would blood, which should be in her body, act against the body carrying it> Because her body is synthetic. She's an android with real, though grown and grafted, flesh covering her mechanical insides, much like the Terminator. Thus the blood, though necessary to feed the grafted skin tissue, then, is not natural to her body. As such, it attacks and neutralizes the acids in her body. Battery acids. She must consume large quantities of lemon, then, to counteract the anti-acidic properties of the blood's basic nature. The constant influx of lemon juice prevents the accelerated wear on her batteries.
This also explains her constant state of confusion. The reason androids disguise themselves as human, the only reason I've ever seen, is to learn about us, to gain information, or as it's called in military applications, intelligence. She's working for those robots trying to figure us out. Trying to bring us down. We need Edward Furlong and Christian Bale to immediately drop her post haste. And they should probably take out Schwarzenegger too. Sure he's governor of California and all, but on at least three different occasions he's portrayed a robot bent on world domination. Ergo, he can't be trusted either.
You have been informed.