"I suppose that's true, too..."

Evidently she hadn't gotten quite that far in her reasoning just yet. Although, with that said... Ritsuka gives Archer a curious look.

"... You already knew that almost the whole time though, didn't you?"

There's nothing particularly accusatory about the question, though. Maybe a little resignation. It just seems like the sort of thing some of the Servants would do, is all. Like, say, Holmes, should she ever happen to cross paths with him again.