I agree that Nica in B3 would be a good deal for everyone (tenants and viewers), they are really good friends, with good chemistry. Unless they plan to have a new couple soon, there is no point in letting a room empty, and it would give room to Belle or Blair.
I don't think moving the shared room problem from B4 to B2 would be a good move, but I really liked the little glimpses we got from Tiana last night during the massage, of a playful personality, and well ... those other glimpses too She is pretty isolated in B4 ... Again, I think everyone will win if she would switch rooms with Monica, who seems to fit a lot more with Rosie and Jas than Sofie ...