who should apply and which way it would be faster

[shopnobhumi]

I am a US citizen and recently my mother came through me as i applied for her.I have a younger sister who is currently in Bangladesh.She is 15 and this May she would turn 16. I want to apply for her.But i want to know as a US citizen if i should apply for her or it should be my mother who is a green card holder should apply.Which process will be faster for my sister to come to US.Please advise.Thank you.

[mehta_agm1979]

you both can file at the same time. Which i would advise.
Your mother should file for your sister..and when your mom becomes citizen she can upgrade your sisters case. When you file it will take longer..but you both should file concurrently..