[LOVE JESUS]

You and your wife are in this together. She needs to be on board with you and if she doesn't feel comfortable taking in another child, then you don't need to take on this responsibility This is extra work on her and really the whole family.
Maybe you could include the young girl in SOME of your family activities occasionally but not adopt her or bring her into your home permanently. I would be upset if my husband wanted to adopt another child if I did not want to do it. JMO