Speak to an immigration lawyer. IMO you will only be able to potentially sponsor the child for PR if you adopt the child and also show that you have been acting in the sole role of her parents for a sustained period of time. So you would want to show the child has been living with you for something like 1-2 years with no contact from the birth parents and you fully provide for the child. I'm not sure how you will achieve this living in Canada. Right now it just looks like an adoption of convenience. Again, speak with a lawyer.