I soloed it as lvl 59 shadow priest after dying once. The trick is to use mana burn untill she has no mana, and you hopefully still do. Then go all out on a nuke. When she tries to heal use fear or silence.

First time i tried i got her down to 1 % hitpoints but she managed to heal and my mana ran out. Fought for about 4 more minutes with little mana, and then died. When I came back I had to rekill all the mobs.

Second time it went better, I killed her, even though I wasted mana on shadow-form in the middle of the fight. Since I was level 59, I got some resists.

I think this was the hardest solo I've ever done, since she's got so many spells at her disposal - fear, full heal at almost no mana cost, mind flay, etc. But when she's really out of mana she only hits you with her fists, which do very little damage.

I used shield, and see no way of not using shield. The post above me soled it with level 58 (!!) mage. I wonder if mage's longer silence was what made it possible at all, becase after main mage nuke, she'd heal and win.

At any rate, using the variation of above is probably a good way to win. Rogues can kick her, but then again she might fear you... Tough cookie.