I think confidence comes by different aspects.
1.In our country, lots of importance is given to Parents status, which Sadhana does not have.
2.Ragini did whatever she wanted, like learning dance which made her confident as getting whatever you want in life makes a person more optimist....But Sadhana probably never thought of her likes as for her leaving under someones roof itself was too big.
3.I feel Sadhana has confidence in herself, but when somebody says you don't deserve this , it will definitely make you wonder when you are so humble.
4.After saying all these I still want to say that Sadhana has confidence..otherwise she would have not made an attempt to learn dance in 3 days or work under.
So here is it not Sadhana's confidence in question but her down to earth behavior, which put everybody else's perspect in front of her own.