The longtime Green Lantern of Korugar, who replaced Sinestro when he turned to the dark side, is arguably best known for her relationship with John Stewart, who mourned her passing for many years in the pages of Green Lantern but who seems to have found himself a new soulmate.
...So of course it makes sense that it looks like Katma might actually be returning to the pages of DC Comics as part of the upcoming Forever Evil event.
At least, that's how it appears. While this could be Soranik Natu--Sinestro's daughter and another Korugarian Green Lantern--it wouldn't be "the unexpected" for an underused-but-clearly-present character to show up in a story that involves her father as an antagonist and several of her Green Lantern Corps teammates vanishing mysteriously. The return of a character not seen or mentioned since the launch of the New 52, though? Unexpected.
If that is, indeed, Katma, the next question of course is whether she's actually back from the dead or if, in spite of claims that Green Lantern and Batman were largely unaffected by the shifting timestream of the New 52, she might never have died in the first place.