Here, I can help!
I couldn't beat her either. But then I changed my tactics. I ran up to her and her spell sequencer fired. Then I ran out of range and rested!
When I came back her Sequencer had worn off, so what I did was hurt her!
Then another one fired, so I ran again! And rested!
Then she was out of spells. I killed her!
Call it cheesy, but it works!!!!