After taking care of the Alien Queen when she sneaks aboard the Sulaco why didn’t Ripley and the others stay in orbit and destroy the derelict ship before leaving?
Bishop's estimation was that the destruction of the plant's reactor would be sufficient to destroy an area that easily encompasses the location of the derelict ship.
RIPLEY: She's alive. They brought her here and you know it.
BISHOP: In seventeen minutes this place will be a cloud of vapor the size of Nebraska.
Since Ripley has no good reason to disbelieve him, chucking a nuke at the surface (after the very visible destruction of the reactor) would serve no useful purpose.
We learn in the Alien: Resurrection novelisation that Bishop was in fact wrong. The explosion was marginally smaller than Nebraska, but he was only out by about 5% and it did indeed trash the derelict.
It was too bad they didn’t have more historical information. Gediman considered it a scientific tragedy that they couldn’t go back to planet LV-426, where the Aliens were originally discovered by the Nostromo crew. The wealth of information that must have been there! But the derelict ship with its bizarre cargo of thousands of eggs had been destroyed when the nuclear reactor of a damaged atmospheric processor had exploded, leaving nothing behind but radioactive waste and a crater nineteen megahectares in size. LV-426 would never be habitable again.