I do not think Setsuna can be compared to Inuyasha. What i believe is that Setsuna is a very unstable Hanyo. Sesshomaru has surpassed his father so imagine how much stronger his blood is. #半妖の夜叉姫+ mini thread

Therefore, my guess is that Setsuna's normal look without the seal and probably even the pearl is like that since birth.
I don't see why else they would be taking such extreme measures with her as to completely seal her demon blood. #半妖の夜叉姫++

She did mention that the blood was too strong, so she can't really control it for long.
Inuyasha was lossing control on very specific cases. Setsuna might be different. Without the seal, she would constantly lose control of it.
#半妖の夜叉姫