Other mistake: In the scene where Ripley throws the basketball at Johner, Christie says to Ripley, "Ok, I've got a new game, tag .." He hits her with the handles straight in the face once, he misses the next shot, misses again, and Ripley hits him to the ground, but you neither see or hear the handles fall. (00:23:15)
Other mistake: At the end of the movie, as the ship is approaching Earth, the Earth is backwards. Africa is obviously pointing in the wrong direction, as if the image has been reversed.
Other mistake: When Ripley pulls the knife out of her hand the blade is smoking as her acid blood is melting the steel, however shortly after she touches the girls face and hands, and the acid blood has no effect.
Other mistake: The remaining crew of the Betty, plus 2 others, have to swim 90 feet underwater. This they do, but once they are out of the water, the only one who is wet is Winona Ryder.
Answer: In Alien 3, Ripley discovers there was an Alien queen embryo growing inside her, so she chose to kill herself. By cloning her, scientist were hoping the Alien queen embryo she had in her at the time of her death would also become cloned, which finally happen after the 8th try. This is also why the Alien queen they extracted from Ripley has some human traits.
Bishop73