The more concerning thing is imho how she managed to defeat all Grands.
Given, the ones chosen weren't exactly ideal in my opinion, but Merlin in particular shouldn't have been beaten at all(Or summoned for that matter). Which makes me wonder whether these were actually the "Grand" Servants.
I also have no idea why they used Castoria as Saber there lol.
Imho A Setup like this would have been better against U-Olga, and the counterforce should know it.
Arthoria, Scathach (If Merlin can be here, she can be too
), Nobbu, Hassan; Rider: Moses or Achilles
Zerker: Herakles or Beowulf
Caster: Assuming Merlin shouldn't have been there, either Abe no Seimei or Tamamo;
Though Tamamo, may get disqualified due to her potential of becoming a Beast.
Grand Adventurer: George Stobbart.
I still wonder how she got Merlin in particular down, at the end of the day she is just a beast, and Merlin has been shown to be able to at least hold the Negative-Abilities back. Moreover, his illusions are literally supposed to fool the planet/universe itself.
But man... This really makes you think what the Holy Church must have in their basement if they don't seem to be too scared of ORT.