OK, so the idea is that Norma was basically genetically engineered and grown to life once the ship landed; the little scout probe-thingie (that green orb) did a little reconnaissance and determined that they were in the right place, and that this is what she would look like. She's implanted with an alien consciousness from her home world, but the body is mostly human DNA with a bit of alien tweaking. She doesn't have, like, tentacles or anything.