Adopting my non-biological Niece??

I also posted this on another thread, but I want to make sure it is seen! Thanks!! I live in Utah but was raised in Washington where all my family still lives. My sister is a drug addict and has lost custody of my two nephew's to their dad a few years ago. She has just recently lost custody temporarily of my niece (she has a different dad than my nephew's, and my niece's bio dad is an addict also). Temporary custody has been given to my Mom who is going for her foster care licence. I think the only reason that she was given to my Mom is because that is what my sister recommended. My sister is my mom's step daughter therefore has no biological relation to us. My question is, my DH and I are preparing to adopt a baby some day in the future and would love to give my niece a good home should my sister loose custody for good (which is very likely). What would my chances be of getting her? On paper, we are the best choice compared to any biological family and she only knows us as her family, she doesn't know my sister's bio family or her bio dad very well at all. I really want to raise my niece and I want to know what my chances would be?? Any input would be great. I am going to talk to her social worker to see what the steps would be and about the cost. Thanks for your responses!!