In light of the PC-98 CRT and merge between Windows era and 98' era, I'll add onto this.
Yuuka has defeated
Alice Margatroid in Mystic Square (PC-98). The latter of whom was able to incapacitate
Mokou (a type 1, 3, and 5 immortal), after inflicting too much pain for her to keep fighting. To reinforce this suggestion, Alice has also confirmed that
Yuuka is indeed stronger than her after defeating her in Mystic Square. It was also confirmed that the time between the events of Mystic Square and Embodiment of Scarlet Devil are not far apart, and that
Reimu was the same age in both games according to her EoSD profile. This is indeed the same Alice that defeated Mokou, and the same Alice that was defeated by Yuuka. Judging by this alone, Yuuka should be more than capable of handling Anna's type 8 Immortality.
If Anna's immortality is going to be an issue, Yuuka is probably going to relish the fact that she can play with Anna until she gives up. It isn't exactly going to be enough against a scalding hot AP shower of endless Danmaku; especially since her immortality seems to be resource-driven (correct me if i'm wrong here). Yuuka is simply going to convert Anna's attacks
into Spirit to regain stamina with her bombs, and keep up her assault.
Other than that, does Anna resist the Space-time Manipulation and Power Modification Hax that Yuuka has? Like all other spell card users, she has
a spell circle that slows things around her to a near stop. Alongside making attacks that would be
lethal or otherwise impossible to overcome 'gamified' with her Power Modification. Dispelling Yuuka or casting insta-death magic isn't exactly going to work out under these conditions. Anna's abilities will essentially become a puzzle for Yuuka to weave through.
The most likely wincon Yuuka has here is simply curbing Anna over, and over, and over. Either until her resources are depleted, or until she gives up.
The funnier thing here is that Yuuka's Fourth-wall breaking can allow her to mock the player, as she has done before.
Voting Yuuka FRA due to a Stamina and AP advantage, alongside attack-altering hax.