After Ripley survives the EEV crash on Fiorina 161, Clemens takes care of her. She stays strong even when she finds out what happened to Hicks and Newt. When she sees a burn on Newt's cryotube, she persuades Clemens to do an autopsy to make sure the child wasn't impregnated. Once her friends are cremated, she shaves her head. Lice is a major problem on the planet.
Clemens tells her about the history of Fury 161 and helps her find Bishop, but she still refuses to trust him. She won't explain why she really wanted an autopsy or what she thinks is going on. She even sleeps with him to avoid his questions although that's clearly not the only reason for her action. She's attracted to him.
Just before Clemens's death, she gets him to reveal his sordid past. She doesn't judge him for it. When Andrews is killed, Ripley takes over. Her first plan to capture the Alien should've worked, but it gets screwed up when the creature attacks an inmate, and a lot of prisoners end up dead.
Once Ripley discovers she has been impregnated with a Queen, she tries to get the Alien to kill her, but it won't. She asks Dillon to do it, but he also refuses. He knows they can use her to fight the creature. Later she helps Dillon convince the inmates to lure the beast into the leadworks. When 85 suggests they wait for some guns on their side, she tells them the truth about the company. "When they first heard about this thing, it was crew expendable. The next time they sent in marines. They were expendable too. What makes you think they're going to care about a bunch of lifers who found God at the ass end of space?"
Ripley lets Dillon use her as a shield to draw the Alien into the mold. After the creature jumps out of the lead burning hot, she switches on the sprinklers, killing it.
The company arrives, offering to take the Queen out of her so they can destroy it. She knows they're lying. She commits suicide by diving into the furnace. "This is Ripley, last survivor of the Nostromo, signing off."