She didn't join Hestia's familia in the SS, but Astraea told her to convert familias in it, and she thought of Hestia's familia so she most likely will convert during volume 19.
You'll be waiting until Volume 19 at least. Astraea had to show up to the War Game so Ryu could participate, because Ryu was still in her Familia at the time.
@ThatRabidPotato If you confirm ryu's entry into the hestia family only volume 19 then it will take a long time. If we know anything by SO 13 . But it would be asking too much