Since they met the once, I think Cassandra would make a point of saying hello to her in the library and seeing if she's all right. Not in the "you are now my responsibility" sort of way, more just trying to be a good neighbor.

If opportunity arises I'd love to thread with the two of them again!

(... And once I get Nepeta into this I would love to have her encounter Fio while playing imaginary games, but that's for later. <.<)