After being initiated, transfering and joining another soro

[Drolefille]

Potentially. It depends on the rules for social activities which tend to be stricter for NPC than for fraternities. Hanging out at sisterhood or philanthropy events or even just at the house wouldn't be uncommon, IF she's good friends with the sisters. Clearly ritual would be out. But that's not the sort of arrangement that you can ask for as the person from the outside.