Did you know? With the right memoria, 4s Shii can solo Despair Patricia!
[*very, very slowly]
If you like watching grass grow and paint dry, then have I got the strategy for you! It relies on Skill Quicken to let Shii continually chain Survive every turn, thus rendering her immortal. You don't need to have her SE totally maxed out, but you will want all of her passives unlocked to maximize her MP gains.
First, you'll need two passive memoria for Negate Curse and Negate Stun to prevent Patricia from screwing you over. There are a bunch of memos to choose from for this, but I went with My Bible and Feigning Innocence School Time because they're what I had on-hand.
Next, you'll need two active Skill Quicken memoria with a 6-turn cooldown. I used Hiding The Real Me and When You Look Up, It's Blue, but any other 6T cooldown Skill Quicken memos will work just as well! They stack, and also affect each other, which is crucial in letting you spam Survive.
The battle itself goes like this:
Turn 1: SE active (Survive), both skill quicken memos
Turn 2: Doppel (Survive), accele, accele
Turn 3: Doppel (Survive), accele, accele
Turn 4: Doppel (Survive), accele, accele
Turn 5: SE active (Survive), both skill quicken memos
And so on and so forth until Patricia eventually dies. It's not fast- it took me an hour and over 110 turns- but it is doable!