Yes it does seem this adoption is all about her - if she cared two hoots about what is best for an orphaned child, she would see that it would be better to help that child to stay with her blood relatives and in her own culture. She could "adopt" her and let her stay in situ for example if she cared that much.
Yes, poverty is terrible but I actually can't see that being adopted by madonna would be that great an alternative. You'd be rich, but that's not everything. And children of the rich and famous, especially if their privacy isn't guarded, often end up as train wrecks and that's even without losing their parents at a young age and being torn away from their surviving family and culture.