"And changed a great deal about our history in the process." Well, a lot more, anyway. "In the end, his actions didn't make a large impact on our future. He died long ago." Back in 1898. Oh but she didn't specifically say which year they went back to, did she? Whoops. She did give him clues about how long a time it's been. The fact that she has to calculate at all suggests that it's been a very long time since she was in the right timeline. The previous timeline, before the jump and her century of hoping she wouldn't mess with anything major.
The implication of all of this, however, is the fact that she's had to relive a good deal of her own history, allow horrible things to happen again, and she wasn't entirely certain how Nikola would take that.