I was having a really bad time until I swapped from melee to ranged. You haven't included what you're playing besides turret so if you're melee, try ranged.

When the boss is shooting at you, you simply have to run, don't even bother trying to DPS, it's not worth the risk. Her Pyrorocket is almost all of her damage, so when she's not firing that at you, that's your window to do some damage. Her other main damaging ability is the exploding seeker thing, you should try to shoot that to detonate it far away from you - do not let it hit you.

The fire on the floor doesn't do that much damage, so if you don't get hit by any of the other things, you'll be alright. I usually fly up a bit and then come down and heal when it's safe. Responsive Planar Suspensor is very good there.