I think Surbhi looked like a very nervous Naagin after her transformation. I mean, uski aankhon me na gussa tha aur na confidence tha. Her eyeballs were fluttering in her Naagin roop. She looked so unsure and horribly docile for a Naagin.
But, one thing is for sure this was not Bani's 1st transformation. And why did she take Noor's form? This sequence smells of a set up strangely, and I hope to see Surbhi pulls off her first Naagin act successfully.
Personally I think Surbhi is very new to Chroma and green screen shots and VFX of a fantasy show, hence maybe she looks so nervous? I maybe wrong.