Did I miss something?

Both Pratha and Mehak said that Pratha was 'chosen' to be SSS Naagin.

When I heard that, I interpreted that Pratha was a normal (may or may not be ichchadari ) Naagin then she was became SSS Naagin. Rising in the ranks of Naaglog... etc..

But then I see many people suggesting that she was a human turned Naagin. I am confused.

Where did it say that Pratha was actually human?

No . They didn't mention that she is human turned into Naagin. Few ppl guessing it that way

The reason being she is not fierce like other naagins the way she said she is scared of rishab none of the naagins did that in the past. Even bani for that matter her husband was a cheel 😆 iska toh phir bhi insaan hai bani was more fierce than pratha considering that people are guessing she might be human turned naagin as that justifies her desh prem as well as this behaviour😆