No, she dives into the water to save Genny. That's her turnaround - she deliberately causes Genocide to fall helplessly into the water, believing that to be the best (or perhaps most miserable) means at her disposal to kill her. It would have been very much her directly making the kill (though I don't think Diana would make that distinction anyway - she doesn't really need to, after all, as she's willing to kill directly, so taking responsibility for an indirect kill should be automatic for her). She spends a moment exulting in the concept, then realizes she totally wants to rescue her, and goes streaking into the water all "Thank all the gods I am not that person," meaning to preserve Genocide's life.