It is best to leave the fine Slytherin custom of allowing your conversational partner to assume facts not in evidence at the door as much as possible. Ekaterina Petrovna did not attend Hogwarts, but you may think of her as a Ravenclaw crossed with a Gryffindor; she has the Ravenclaw intellect and the Gryffindor intolerance of fools and willingness to say so outright.

And of course you may ask.

I can't recall -- which one sponsored Mr Weasley? Avery? Montague?