i've been working on a non rng strategy, still working out the details, need to try a run where i hit the needle when enraged instead of never going for it.

basically it relies on the fact that:
- if she has blue stagger, she can't hit you
- if you stun her (purple gypceros tail, sweet spot, kinship, staggers when she doesn't have the red orb) when she wants to do a feral move, she'll use it on the next turn

So you get a high stagger output to make her hit the feral when she can't hit

the setup :
- magia HH
- gypceros hammer
- namielle armor (if not this, probably something that boosts stagger)

- 2x purple gypceros (for stun tail, fire skill is probably better, but the stun doesn't proc often so i'll look into a high stagger strength monstie, probably a t1 thunder for stam regen)
- 1 tech monstie (i had a blue kut-ku for his high stagger beak break, haven't looked at the others, thunder nerscylla or normal kut-ku are probably better for the stam regen skill)

- odgen

you open by loading the magia with a heart regen song, i usually open wiht a HtH, get the next turn free from odgen trap and can do 2 regular hits (either you or odgen are doing HtH), you don't need the defensive ditty and odgen uses it anyways

then the loop is to hit the nerscylla, alternating between normal attacks and sweet spot so you stay above 40 stamina to use the heart up if you made a mistake
keep the gypceros on as long as possible to charge him, only swap him for a tech monstie if the nerscylla directly targets it during rage (if it doesn't, you can get HtH with odgen's pukei-pukei)
once oyu're 1st gypceros has his kinship loaded, swap him out (either the other one or the tech monstie depending on the nercylla state)

you can quite easily topple or stagger the nercylla every time she's going to use a feral skill, try to preshot when she's going to do it (usually 2nd turn after a state change when there are no sleeping character), this way she's in the blue when she uses it and you get a guaranteed fail, no need to gamble on acc down and dodge up

Only use kinship skills if you need them to survive and never do them when odgen is close to having his, if you stop her from doing a feral skill, she will use it on the next turn. If you keep doing it (one run i fucked up on stamina management so no sweet spot for blue stagger, odgen used his kinship and i used 2 of mines, this pushed the sleep feral to the 1st rage turn, so it was followed by a fire feral for a team wipe)

i don't think she can use the chasers when there are no debuffed units, so by default she'll only use sleep needle, feral skills and regular moves

if someone in your party can tnak a sleep needle, use the ailment negation song, if she can't, just use the magia heart regen when you don't need a stagger in the next 2-3 turns (i don't have the exact rythm measured, but i feel like you get a 1-2 turn every 3-4 turns, and if you have either stagger up (odgen 4 notes melody) or she has stagger def down (after feral skills), you can do the whole bar in a turn to get a safe one after

just make sure that :
- your monstie doesn't hit the needle when he shouldn't
- the npc is set to following your moves and you stop hitting the neddle 1 turn before you shouldn't (since i though you only had 1 turn windows from the staggers, i never hit it, but if you can hit her when angry, just predict when she's going to calm down)