The first two nonspells are already very Lily-like. A change in colour makes them look rather autumn-like, but still retains the style that Lily has in her original danmaku. Great nonspells.
The focus then shifts to Letty, which shows off some of her ability corruption as well. It's nice to know that in this double battle, one character isn't taking all the spotlight. Spirals like I see in this spell are definitely something that Letty would use, and I can definitely agree that an oppositified Letty would use a vortex of fire.

The fog clouds in Letty's nonspell have turned into... heat haze?! I sure hope that's intentional, because if it is, it's really clever!  The graphic should probably be re-coloured to have a reddish tint though. Just a nitpicky thing that just adds to visual factor. Very faithful to the original Letty's danmaku.
I can see what you're trying to do with the spellcard immediately afterwards, but it could be a bit more exciting. I like where this is going though!

For the third spell, I think it'd be better if you lowered the damage resistance. It's dragging on for a bit longer than I would like.
The last spell is... well, it's chaotic, I guess. I can't really pinpoint what it's going after. Rather anticlimatic, considering the really strong opening patterns...

I also died to Lily's last spell after like, three waves, so I can't judge most of it. It's... Lily-like, but it got a bit repetitive after a while. Variations on the same few seconds of dodging isn't all that good for a last spell...

... Anyways, besides that...!! Let's take a look back at the script in its entirety. Both the danmaku and effects are quite stunning, and the characters keep elements of their original danmaku while adding new aspects to show what they've become. I dare say this is one of the scripts that reach such a level that it is eligible for being featured~