The underlying hostility of those she leads. That wasn't in Aliens - she earned the marines trust by driving in after them.
But it's more the attitude of "We have to kill it". There's no escape in this one. In Alien it's we have to kill it; no, now we have to get away from it. In Aliens it's much the same. Problem comes halfway through the second half when she finds out about the Queen she's carrying. The attitude has to shift from "We have to kill it" to "We have to kill it AND me". Gone is "I got you, you son of a bitch" and "Get away from her, you bitch" defiance and it's replaced by "I want you to kill me. No prayers" resignation
She goes from someone who will fight to the very last to being resigned that she's going to die. In the workprint, the old attitude resurfaces when she considers Bishop II's offer for 40+ seconds. In the AC and TC the decision is made more or less in an instant and there's no consideration of going back.