Quote from oran250
There surprisingly easy to kill if you use the right weapon like a sword.Do not try kill them with a bow because when your pulling it back she will through a potion at you so use a sword and dodge her potions to kill her.
A potion can be thrown a maximum of 9 blocks, while shooting a fully charged bow can reach 25ish blocks. As long as you keep your distance, she shouldn't be able to hit you with a potion. I still think using a bow is the best solution to fighting a witch.