>>531566918
Here's a breakdown I wrote in the previous thread
>>531556487

Basically the TL:DR is with positive SP, you're tanky, with negative SP, you deal lots of damage
Use her defensive skill to gain a buff that'll tank your SP and keep it tanked
Use it again to get a stronger buff
Use it a third time to eventually swap back to positive SP after using her S3
She naturally maintains at -40 SP and, once per encounter, prevents herself from hitting -45