This ended up taking three tries for my level 144 5/5/3 Ghost. The first match saw Widow getting a horrendous cascade that left her with over 40 AP after her first move. I stared sadly at my own 3 AP and knew bad things were headed my way. They were indeed, as Widow took me down less than six turns later, leaving her barely scratched.
Round 2 was a great pitched battle, and I lost when she was down to 65 HP. There may have been a few bad words involved.
Round 3 went the complete opposite, and I started out getting enough purple to go invisible within a couple of turns (I hadn’t managed to get enough purple to go invisible in the previous two attempts). After that it was not long before an invisibility-fueled kick sent Widow straight to the canvas for a nice nap.