For me what worked first try and had me hardly take any damage was staying between her tails, turn as she turns to stay behind the whole time and using charged r2s (hunter axe) into the back half of her body seemed quite safe and the fight was over in a minute or two.

I know the head is the weak spot but sometimes dealing less damage in exchange for being in a safer spot and taking less damage is a good approach

Plus you can summon help near the entrance to the boss room if you want

Staying between her tails and moving with her to stay behind her the whole time worked for me to first try her. Just stay behind where it's safe and hardly take any damage, I know the head may be a weak spot but sometimes avoiding damage is (often) more important and staying behind her works great for that, I only used a couple vials the whole fight

Beast blood pellets work wonder. I'm lvl 82 and using Ludwig's +8 transformed and with one pellet she went down before she could even summon her damage field.

I summoned both Gremia and Wallar for this, not sure if it affected anything but in the latter part of the fight when she's got the barrier up, on two occasions she charged me near a wall and then just sat at the wall idly taking damage from her own DoT. First time, I hit her to see what was going on and she snapped out of it and continued the fight, the second time I let her sit to see if it was a time thing, she ended up killing herself from about 20%, was a nice relaxing fight for me though.

Did this standing between her tails while spamming the charged attack with Kirkhammer +9 and bolt paper. Summon the hunter npc, he'll tank her for a while and you can just focus on attacking.

Go straight behind her, buff with Bolt Paper and hold L2. Summon the Mensis guy so he can lure her attacks more often. Best strategy there is IMO, beat her on 2nd try

Using the greatsword L2 of LHB +9 I managed to continuously stagger her with each hit. Spamming this would deal 1.5-2k damage (depending if I clipped the head or not) per stamina bar and when I was nearly done I ran round the back and performed a charged R2 with the last of my stamina for a single 1k damage. Rinse and repeat and make sure to dodge the arcane attacks.

I used to think this boss was stupid hard, then i bolt charged +7 beast claws and more or less spammed her tail for the entire fight. I managed to cripple her at least 3 times with 60 strength

I used a +8 church pick and annihilated her, not sure if I was over leveled. I just pressed the attack and had high rally. I remember this boss being a lot harder.

I've been going at it with the Kirkhammer, but I find the 1h sword deals significantly more damage, as she is weak to thrust damage. I've got a +9 Kirkhammer with about 42 STR, and I'm dealing just over 1k damage with a charged R2 to the head. My problem however, with the sword, is that the first two swings are horizontal, and will not strike the head if she is standing up, which the hammer will do much more frequently, though this should not be much of a problem as it is much more efficient to get a few swings with the sword into her chest while trying to bait out a head slam, and following up with a charged R2 to the head. There are other advantages to the hammer, such as the stagger. I find it's much quicker to open her up for a visceral to the face with a charged hammer R2 in the head, but bolt paper on the sword is just as effective, if not more, for this.

Get behind it and spam R1 with mercy blades +10 and beast pellet. Not even a challenge.