Another Earth/WMG

Earth 2 is a doppleganger world.
The moment after the film ends, the Earth 2 double of Rhoda mutates into something ugly and devours Earth 1 Rhoda. It turns out that Earth 2 mimics planets and their populations to feed on them. This is why it took a while to establish contact, and why the Earth 2 SETI woman's voice was choppy - the planet was still manufacturing doubles en masse as it scanned earth at higher and higher resolution. Earth is totally screwed.
 * That's an awesome idea. Please, somebody do a movie with this premise.

The final scene when Rhoda sees her double is actually on Earth 2
Either one could be the Earth 1 Rhoda.

The character of Rhoda isn't actually as attractive as the actress playing her.
We can't call Hollywood Homely because it's never stated, but a woman of 22 years old and being that pretty should have had guys asking her out and trying to include her in their social lives. So maybe she really wasn't very pretty.