Tigra and Greer are two separate personalities. The problem with The Cat series was the fact that the series should have had Gerry Conway writing the stories. The focus was placed too narrowly on the young female readers. Most of the female readers are in the Amazing Spider-Man camp. Thus, if The Cat was placed in Spider-Man's world, Greer would not had been made into Tigra. On the otherhand, Black Cat (as we know her today) would not exist.