I am neither Butch Francisco who rightfully tagged movies according to number of stars depending on how it fared to the viewing public's preference, nor am I like MobilityReel who reviews according to artistic content, plotting complexity and cinematic technology. So for this entry, let it be cleared that it isn't a movie review, neither objectively nor unwittingly.
My arcane purpose though is to cite content improbabilities based on the light of a scientific fact.
1) There is a second Earth. If the fact that there is a second Earth with exactly similar geographical features, same meteorologic strata, same atmospheric condition, and absolutely same inhabitants, it has to come from an Extended Universe. It's essentially the same universal sphere that we belong to, only that it is too far that we couldn't see it. Ergo, if there is a second Earth, we will never see it(unless we have come to a point of technological maturity that we have mastered the science of interstellar transportation).
2) A second Earth suddenly appeared close to the Earth. All planets are "gravitationally locked" to their star systems. There is no way that a second Earth was flung out in the vastness of space, only to have been captured in our Solar System. Even if there is one, we would have progressively spotted its trajectory to our orbit, a lot like how we spot meteors, comets and other NEOs(near Earth objects). And speaking of meteors, if this second Earth is hit by a meteor, causing it to have flung out of its orbital path, it would have earned crust scars and inhabitants and all symbiosis of life would have been destroyed. Ergo, the lead character would never have met herself in another Earth.
3) A second Earth orbits beside our Earth. From the previous statement, if there is a second Earth drifting in the vastness of space that will be captured by our Solar System, by gravitational law, it will orbit right beside a planetary body with the biggest mass. Ergo, the second Earth would have been orbiting beside Jupiter.
4) A second Earth orbiting very close to Earth without adverse effect on the Earth's geologic condition. You know what happened when a Moon gets close to the Earth? The gravitational tug will create a tidal bulge. Oceans will rise and seismic activities will heighten. Now imagine if another celestial orbit, the size and mass of the Earth comes so close to the Earth, imagine how detrimental it has on our environmental geodynamics. Tsunamis will occur, volcanic activities stirred than normal, tectonic plates will be disturbed. Ergo, either our life or the second Earth's life forms would have been destroyed by its coming.
5) A second Earth pops up into existence close to Earth. Since we have debunked the possibility that the second Earth will suddenly appear to us without noticing its primrose path, or the likelihood of it to halt on Earth's orbit having the median mass in the Solar System, let's take into account the astrophysical probability of a multiverse. A universe close to our universe but remained intangible because of a dimensional parallelism. Now, for the second Earth to pop up near our Earth in an instant, the civilization of that second Earth should be far more advanced than our very own. They should have mastered the aspect of harnessing the powers of the cosmos by blasting a gaping hole to our dimension for them to pass through and appear on our Earth at an instant. A civilization this advance would have known and poked around our String Theory, which is so far one of the most difficult but grandest scientific exploration of our time. Ergo, the people of the second Earth would never be like our very own, they would be highly evolved beings.