Adopting my niece from Venezuela

Hi all, I have a 15 year old niece that is having a hard time in Venezuela. She is a very smart child and (wife and I) would like to bring her to US for a better future. I am a US citizen, wife is in the process of becoming a permanent resident. Question is, would I be able to adopt her legally, with her parents consent and bring her to the US? Does my wife need to adopt her also or does it suffice with one parent? And lastly, what kind of lawyer should I get for this?