A Question

Frankly, I wondered about the same thing (for a short while) as I was watching the film. Later, as the film turned to other topics, I more or less forgot about it.

That's probably not the most important detail in this film. But "technically speaking" I think a chaste woman like Viridiana would certainly know if she has been raped or not (maybe a prostitute would not notice it). I think the filmmakers were trying to convey the idea that it didn't really matter for her if the rape actually took place or not. It was already a sin, in her mind, to be in a situation like that.

Even if she felt no pain from having her hymen broken, she could have looked at the sheets for blood. That is what the maid did.