Jinko is really hard, I won't lie. I balanced her to be the equivalent to a "Hardcore - Lite" boss, that you happen to run into early on.
A key element to surviving the fight, and for playing the Warrior in general, is knowing how and when to bounce between Defender and Berserker states. If you get targeted by "Piercing Gaze" she's going to use Queen's Claw on you to both make you bleed and deal some serious damage.
Ideally, you want to open up that turn by going into Defender, and probably using Mighty Guard. Keep in mind that the Warrior deals increased damage the lower her health gets, capping at 50% for Cleave, 75% for Charge, and having no limit for Whirlwind.
If you fall below half health, be ready to shift into Berserker and use Cleave for a ton of damage.
Also, remember that Iron Will will remove nearly every status ailment, and restore 25% of your HP. Never let your Bleeding get to Level 3, as Jinko will begin to use "Relentless Pursuit" which hits twice for some crazy damage.
Additionally, keep in mind that Miller Lite is with you!
Healing Wave is a decent heal, but if you protect someone with Mystic Rune (which halves all damage) first, it will deal double healing.
Gale Blast can keep Jinko slowed down, while Flame Strike deals MASSIVE damage since Jinko, like all Beasts, is weak to Fire.
Use your Healing Salves to try to keep Miller Lite and yourself healed up and cut back on the turns you're bleeding, since Jinko, again like all Beasts, will enter a Frenzied state if you are Bleeding.
Also, keep in mind that when she hits 50% of her health, Jinko is going to use an ability called "Rupture"
What Rupture does is:
1) It will deal 20% of your maximum HP in damage
2) It will inflict a "Level 4 Bleed" state called "Rupture" that deals 25% of your HP each turn for 2 turns before evolving into Bleeding Level 3.
3) It will hit both Angel and Miller Lite.
Rupture is a very powerful attack that gives you a massive panic window. Immediately shift to Defender and focus on healing. Once Ruptured becomes "Bleeding Level 3" quickly use Healing Salves or Iron Will to remove that state.
Keep in mind "Ruptured" cannot be removed by Iron Will or Healing Salve. These two turns are pivotal for defeating her, as she will only use Ruptured one time.
Since you are level 6, you also have access to "Determination"
What Determination can do is help you prepare for Ruptured. As Jinko gets close to half health, be sure to use Determination and get that buff going.
Determination costs nothing to use (now) and will regenerate 60% of your Maximum HP over 5 turns. This totals out to 12% of your HP every turn, which cuts Ruptured nearly in half. You can also use Determination to keep that sweet spot near 50% HP to get maximum damage out of Cleave.
Hopefully this will help. Jinko is a very tough encounter very early in the game, and is meant to really push you to learn the ins and outs of both the Warrior Class, having a teammate, and managing status ailments.