[Altima of the Gates]

The thing is, Ilya is kind of fatalistic. So I doubt she ever mentioned her predicament even until the end. Heck, I don't think Shirou is even aware she is

Spoiler:

a homunculus in the epilogue of the Fate route. She is known to keep these things hush-hush until people find out or its brought into the open. Note that she never tells Shirou herself that she was the grail, even when they started to live together after Berserker was defeated in Fate.