Need advice

Hello everyone. I am considering adopting a special needs child from the DRC. The only problem is the special needs are unknown. Multiple attempts to get a diagnosis have not given much information. Here is what I know about this little girl. She is 4 yrs old and she interacts with other children. When an adult interacts with her she shuts down. No emotion at all. She allows adults to touch her and hold her, so she does not mind the physical contact, but she is always on her guard with adults and emotionally blank. When considering adopting her, I guess I am most concerned on if this shut down behavior is a sign of RAD or other very serious psychological need. I am prepared to handle attachment issues, but I do have 3 1/2 and 6 yr old boys at home and I do not think I am capable of handling RAD or other agressive behaviors. I am told she is not aggressive with other children in the orphanage. Any advice would be appreciated!