Survivor's Curse a few time will drop her resistances (even at level 1) and make elemental attacks much more effective. Blind would be handy to get a preemptive strike in. Alternately, drink a shadow potion when she blinds you to wait it out, and switch to area effect skills that do not need a target, such as Hell Spikes or Elemental Hail.
As for strength potions, if you drink a lot of them, you can do a lot of melee damage (as long as you can hit her).
josie, part 749Mage spell books can be bought, so you could try to find some of these that way.
Chasing Josie... techniques for defeating Josephine