First things first, you should Always pray mage....It's best to have quick prayers set because when she shoots a purple fireball, it will disable prayers.
Always dodge the fireball/ move 2 spaces over that when she spits in the air, if not it will one shot you or , x1 space over will do half damage to health.
I prefer to always walk here for the acid pool and walking/being close to her, makes the flaming fire ball fall a bit slowly. another reason I personally prefer melee on this boss.
*You don't have to spec the boss with claws can use a DWH or BGS to drop defense or another other spec weapon just for damage.
Like all dragons he is weak to stab and can use any stab weapon.
Also when she freezes you she's untouchable until you kill the little undead spawn, you can negate damage by killing her before she touches you, or just tank the damage witch is random but it can max up to 30 HPTS, Hope this provides some help to those in need with this boss.
Regards,
Gambino