Star Trek: 10 Things You Didn’t Know About The Duras Sisters

The sisters were always a part of the Generations script. In the final version, they are associates of Malcolm McDowell's Tolian Soran. 

Conspiring with the El-Aurian scientist, they planned to acquire trilithium in another attempt to take the Klingon Empire, though they are ultimately destroyed by the faltering Enterprise-D in an explosion that looks oddly familiar if you've seen Star Trek VI.

In earlier versions of the story, their tale was significantly different. 

An original version of the script, which was quoted in Larry Nemecek's Star Trek: The Next Generation Companion indicated that the crew of the Enterprise would need parts to repair a shuttlecraft at one stage. The sisters would also have crashed and Data was sent to negotiate for the required items.

The android would return worse for wear after his encounter with Lursa and B'Etor having an arm drop off but managing to secure what was needed by the stranded Starfleet crew.

Of course, there is a deleted scene from aboard their Bird of Prey in which Soran tortures Geordi La Forge for information on trilithium using an invasive probe that affects cardiac performance. The scene also makes much more sense of the retained line that the chief engineer's "heart just wasn't in it..." when B'Etor inquires if Soran got anything out of his prisoner.