She's the Mash from the timeline where she didn't have the guts to put the shield in front of Fujimaru before Goetia's attack. She made a deal with Goetia and became an edgy murder machine to revive Fujimaru. She's fully aware that Fujimaru would hate her for this, but she lives to see them calling her out for all the crap she's done (mostly for the minor fumble that started it all). Apparently the main obstacles she faces throughout the story are Hannibal, Caster Scathach and old man Ieyasu.
Her Class is listed "Shielder (usually disguised as Avenger)", Name is still Galahad and region is listed as the Solomon Singularity/Chaldea.
First Class Skill is the usual Magic Resistance A. The other Independent Action A+, too blurry to make everything out but it seems she only has it this high because of something about how Goetia modded her Saint Graph.
Personal Skills are Psychological Investigation A, Accursed Blood Stigma C+ and Yearning for the Final Moments B+.
Psychological Investigation is a Skill to see through the opponents psychological weaknesses and crush their hearts manifested by her NP. She developed it from how much she ran away from her own weaknesses. In "gameplay", it leaves the opponent weak to Longinus.
Accursed Blood Stigma is Longinus' attacks being painful and unhealable. For 3 turns, her attacks inflict Curse and the opponent gets a Buster debuff.
Yearning for the Final Moments is the never give up Skill. Wordy description of how Mash only noticed her feelings after it was already too late. Merits: Buster buff, attack buff, Guts. Demerits: defense debuff, debuff resistance debuff, Stun the next turn.
Her NP Longinus (The Heart-Rendering Holy Spear Bloodwashed) is A++, Buster and Anti-Human/Anti-Heart. Goetia made it using Galahad's Servant data as the blueprint and Fujimaru's soul as the material. The spear crushes stuff (including metaphorical hearts) causing literally unavoidable death. Normal Mash would use it as a drill attack but Mash Alter doesn't do the drill attack because she doesn't feel too good about using Senpai as a weapon. Since her Longinus is just Goetia's replica, it's not as good as the real Longinus.