First a warning: you lose the key item you had to run around the past putting together on entry. You will probably have to do the whole run again if you lose so go in prepared with as many people as you can manage.
Form One:
Like mentioned before her attacks are magic based and knockback. My group had a pld tank up against a wall, although her attacks would hit for a decent amount. She casts mostly enfeebles, although breakga can be troublesome if it hits too many people.
Her WSes aren't really much bother although I believe one of them will dispel buffs. The charm is definitely gaze based and not hard at all to avoid.
The one trick is she casts Meteor, 1200-1800 damage, so try to keep everyone out of range. If you're tanking against a wall, you might not be able to outrun it. She may only cast this at low hp levels and despite meteor killing a few people we were able to finish her off.
Form Two:
You spawn in far away from her and she doesn't aggro so you have all the time you need to rebuff and get people out of weakness.
Gets a bit trickier now; we didn't really try to full tank this bit, our damage came from 2 smns and avatars held the hate for most of the fight, with the pld only stepping in when smns had to recast or when things went pear-shaped.
Her WSes in this form are Dark (element) named after the AMs; Dark Flare, Dark Quake, etc. They do hefty elemental damage (400-800), at least to avatars, in what looked like a frontal cone, and occasionally she will use two back-to-back. In addition to these, we saw Dark Moon, which inflicted weakness for a short amount of time.
Her '2hr' such as it is, is Dark Sun; she gives a line in /say before using it but there's not a lot of warning beyond that. Dark Sun is AoE death, like Zantetsuken, at about 15' (but that's not definite) so keep everyone scattered and out of range when you're bringing her below 50% or so.
We didn't see any nasty moves at 25% or below, just more of the same.
One thing that's common to both forms is that she will summon adds called Elemental Gyres; despite what the wiki says these will show up at any hp level. I have no idea what they do; they are completely stationary and take no action. We assumed that they might do something if we got too close to them so we gave them a wide berth and they did nothing the entire fight.