Played 80 games against Lewena: 4 decks, 20 games each. This deck had the most success.
20GP: 11W, 5D, 4L (55% win rate, 80% win/draw rate)

Protect your aces - especially protect Lightning's A from Ifrit whenever you can. Use your 1s to take her Terra Branford and Onion Knight. Y'shtola often works well against Cloud.

As is the case with all Chaos rule NPCs, expect a lot of finger crossing. Without fail, if you play Lightning first, they will play Ifrit first...