She's beautiful.

I really don't have much advice but have you tried putting Sammi and Ritchi up in a room or somewhere with the door shut and let Samantha have a little time to roam by herself or with Vos? I think making her comfortable up stairs might help the situation.

One thing I've learned with introducing new cats to the house is that it take time, some times a lot of time.

Hopefully you can get more and better advice here. Good luck and thanks for sharing the picture of sweet Samantha.