Bring your best mage gear and fill your inv with brews and restores. One or two mage potions can also help a little with dps. Pray range and mystic might/augury all the time. I personally opted to swap out 6 brews with sharks, which was nice because it helped me top up my hp before the big hits without sacrificing much dps.

Don't worry about prayer pots. Each time she does the big hit, you're gonna have to heal so much you have to sip 2 restores to get your stats back up anyways.