Well, we already know Shree will be having twins, one good and one bad.But will she have both boys or both girls? She will have one boy and one girl.Girl who is the good one will be named Naveli and boy who is Kangna's bad ansh will be named Rudra.Since, Naveli is a girl Shree will be compelled to think she is Kangna's ansh.
Ravs and BC- I think the basic premise is initially Shree will think Naveli is the evil child....circumstances will created by Kangna to make Shree think that so her evil ansh will be protected.