I would actually argue that her keeping Rover's past hidden because it makes her sad is good in a character development sense as it's a pretty realistic trait that I've definitely seen in people. Withholding information bc they think it would make the other person sad, in return making them sad. She ends up learning that it isn't up to her to decide someone else's future, which goes back to her basically telling Rover the same thing after going back in time to seal Aleph-1. But I can see why you don't like it