Matrix/Supergirl

Post-Crisis / New Earth
Matrix was duped into a "loving" relationship with Lex Luthor, not knowing his evil true nature. She also fount herself the unrequiting recipient of the affections of Jimmy Olsen.
 * 1)  Comet  - Apparently she had a thing with this character, described as "a bisexual suicidal female comedian who could change into a male centaur that was once a crippled male jockey." It's also stated that this was due to Comet's "love powers," so I'm not sure it counts as an actual romance.
 * 2)  Clark Kent / Superman (of an alternate Earth-One)  - Matrix traveled to this alternate universe, much like the Earth-One of pre-crisis days, where she replaced the Kara Zor-El version of Supergirl in coming to Earth. She and Clark fell in love, getting married and having a daughter named Ariella. Eventually, however, Matrix was forced to return to the normal universe, leaving her husband and daughter behind.