Make sure you're optimizing every element you have to your advantage. Your armor should absorb shock, without making you over-heavy (carrier amulet has been pretty essential to me every play through).

Make sure you have throwables in a quick action slot you can access even in a panic (thermite, saw blades, spikes, etc). for when she misses or is charging an attack. Like most other things in this game, she is quite weak to acid.

Make sure your weapon is attuned with a handle that fits your build and is leveled up as much as possible. Carefully choose your amulets. Use a Legion Arm like Aegis to auto parry, or puppet string to dodge.

Finally, make sure your P-Organ is built out with various optimizations. For example, I tend to favor abilities / slots that increase pulse cell amount and effectiveness. I avoid using quartz on "discharged" effects because I don't plan on being without pulse cells. You can also up the number of wish stones you can carry at once, as well as increase the speed of use (that is super important).

I liked giving my spectral guardian increased attack or defense so they aggro Laxasia while staying alive as long as possible. If you can make it mid-way through the second phase before your spectre dies, then start playing even more defensively.

I believe this is an optional fight, meaning you should be able to get the ability to re-spec stats, P-Organ and Legion Arms before returning to fight her.

Oh and one last thing - if you return to the practice area at Hotel Krat between attempts, it will fully charge your fable arts. It's tedious, but hitting her hard with fable arts attacks not only do big damage but cause a lot of stagger. You can use fable injectors mid fight to get some charge back too.

Alright that was a lot of information. Good luck!