The perfect moment would have been right as she was disappearing. That said, even if not a twin and is exactly yourself, still would be cringe and creepy.

To be fair, it was a whole team plus the numerous Reverse Flashes in one area, so I'll give that one a pass. Also, may not make a difference, but he with into the future instead.

Having a speedster on their team would have been nice, but I don't think they nerf him and more like they made him more full of himself.