On my 1st playthrough using my old team, I beat her first try. I had items and affection on my side though. On my 2nd playthrough, I had a different team and no items in battle. I don't remember whether or not I beat her on my first try, but I did win after a while. Her team still has those old flaws but is still put together really well, and I had a ton of fun fighting her. Both times challenged me a lot and had to make me think. The AI being good and using abilities as well as possible was really cool, since you don't actually see that a whole lot(ex. if you spam water moves on her pokemon, she'll switch to storm drain gastrodon).
Don't really need to get my ass handed to me 7 times to get challenged, and Cynthia is a perfect example of that. Probably one of the best champion fights that don't want to just throw a bunch of bulky waters or dragons at you.