I want to know if that is possible, or maybe I have to ask for legal guardianship instead?? I want to bring her to US and offer her a better education, I'm 22 and my (colombian) parents totally aprove it. What should I do?

Are you qualified to be an adoptive parent in your state? Legal guardianship will not get her any long-term US immigration status.

What is your family's goal with her? A US education? Please be more specific.