is proven!

SALVETE OMNES.
First, thanks to everyone who answers my posts.
Second, I need the Latin for “is proven!”.
I’m trying to write “The chastity of Diana is proven!”
This is all I’ve come up with:

Castitātem Dianae vēra est.

MVLTAS GRATIAS ET VALETE BENE.

castitas Dianae probata est would work

Thanks benissimus.
But this leads me to a second question…
Why is “castitās” in the nominative? Shouldn’t “castitās” be in the accusative to show that it is being possessed by Diana?
Unless I’m declining this incorrectly :question: :

castitās, castitātis, f., chastity

castitās
castitātis
castitātī
castitātem
castitāte

In the passive system, the thing or person receiving the action is in the nominative. Do you say “I am proven” or “Me is proven”? (just for the sake of an English analogy)

Ah, that makes sense.
Passive, Parasyllabic… I’ve got a lot to learn.
Many thanks!