After she hits a successful ult and eats someone, she'll be vulnerable during her eating animation for a good 2 to 3 seconds. This time is more than enough to burst her down as she won't be able to use any of her abilities during this animation
Place one illusion behind Evie if you can, keep shooting her, till either she leaves or you get low, on low health teleport to the illusion, keep shooting her, it will give your allies time to get to you.
This match up depends on your timing and his aim. If you get lucky and time his shot with you obliterate his follow up shot won’t be enough to win the fight.