More thoughts on the "when" of Riza...

Established player characters she's met: Cornelia, Malserrin, Nicholas, Nityana

Characters she probably hasn't met: Sakura, Lysandra, very likely Benjamin, unnamed deceased brother (died on the Pattern some few decades ago).

??? and NPCs: Michael, Farwaiyn, Cornelia's friend Brand, deceased brother Desmond.

If she knew Desmond, and if Desmond is the same one Farwaiyn was close to, then we've got a circle of knowledge that may be either mutual or one-sided. (Riza might never have met Farwaiyn, but Farwaiyn might know of her through conversation with Desmond).