At the Super Buddies message board, there's a user under the handle "NightwingTAS" who builds digital figure models off the Bruce Timm DC Animated Series template for further fan fiction adventures of his own devising. Number 8 in the "Z'Onn "Z'Orr" series, here's his take on the Post-Crisis "Supergirl..."
The protoplasmic entity known as Matrix came to New Earth from a pocket dimension. She was created by that world's Lex Luthor using Lana Lang as a template to save the Earth. When she arrived on New Earth she was near death and nursed back to health by the Kents, where she took the name Mae and fought alongside of Superman as Supergirl. When she heard screams Supergirl found Linda Danvers who was near death and in order to save the young girl she merged with her, and the two became Supergirl. As this new Supergirl they discovered that they were the Earth-Born Angel of Fire. The two seprated when Linda had Mae merge with Twilight to save her life making Twilight the new Earth-Born Angel of Fire. During a fight with Lilith the two were seperated leaving Twilight as the Earth-Born Angel of Fiire and Mae near death. Superan brought Mae to Star Labs where no one could figure out what was wrong, then J'onn recieved a strong psychic yell he formed a link to her mind and figured out how to save her. Mae was created by using DNA from Lana Lang and a Yellow Martian creating a new form of Martian. J'onn helped Mae master her true powers. Lana allowed Mae to move in with her and Pete as her cousin Mae Lang and J'onn gave her a true Martian name, M'ae L'ang.For some reason, Supergirl and Martian Manhunter intermingle in a number of fan fictions that I've encountered. They had one team-up in the '70s, and that's about as deep as their relationship in the comics goes. While I'm a fan of the classic Maid of Might and the supernatural Linda Danvers Supergirl that book-ended the Matrix period, the Matrix itself was kind of a moronic, emotionally unstable pile of other-dimensional goo who played sex doll to Lex Luthor. I'd rather not see J'Onn stuck with literal cast-offs from a Superman satellite player, and I especially don't want B'rett involved. Anyway, do click on the link to see an alternate, Caucasian Martian version of the Matrix, and if you think that we don't love Kara Zor-El around here, just ask our buddy Anj at Supergirl Comic Box Commentary.