Fridge Logic: So Sarah's reward for atoning for her sins is...spending eternity completely alone on a tiny island in the middle of an eternal ocean? And not even the whole island at that; it's too densely forested to even walk between the trees maybe 25 yards from the coast.
Judging by the ending cheesecake shot, she's doing quite well for herself. Set up a camp, a fishing line, and got that bikini from somewhere.
Or alternately, the trees seen when back up in the ship were so dense because the artefact could only project a small portion for our heroine to explore. There's no telling what the real beach at the end was like, though we do see her amongst some flora during the Fanservice credits.
It's better than the alternative endings....
I just assumed the escape pod had a tracking device, so she'd be rescued eventually. Given the fact that it seems that humanity has spread acoss the galaxy, you'd think this'd be a given.