The Post-Crisis version of Supergirl appeared primarily as a supporting character in Superman comics from 1998 to 1996.
Superman: The Man of Steel Vol. 9
Collects Superman #19-22, Superman Annual #2 and Adventures of Superman #441-444, and Doom Patrol #10, originally published 1988.
The mysterious new Supergirl meets Superman for the first time! Plus, the Man of Steel faces Mr. Mxyzptlk, runs into the Doom Patrol and battles Metallo! And Lex Luthor is tricked into releasing criminals from the Phantom Zone — and it’s up to Superman to clean up his mess. Plus the triumphant return of Guardian & the Newsboy Legion in a story that will impact Superman and the City of Metropolis for years to come!
Superman: Panic in the Sky
Collects Action Comics #674-676, Superman: Man Of Steel #9-11, Adventures of Superman #488-490, Superman #65-67, all originally published 1992.
This new edition contains 4 more issues than the original trade.
Brainiac returns to invade the earth with his ultimate weapon, Warworld, a planet-sized satellite built for destruction. With the help of super-powered friends like Wonder Woman, The Flash, Green Lantern and many more, Superman must lead the attack on Brainiac and protect Earth!