Yes, the child needs a B2 visa to be able to enter the US for the N600K interview. With 2 USC parents, one already with a US job, it's going to be tough to convince the consulate that your family has no plans to move to the US.
As others mentioned, your child's case seems to be textbook IR2 for adopted child, so just go through the I-130/IR2 process. After your child enters the US with IR2, apply for her US passport and N600. No need for N600K. Plus, with IR2, you have a chance at an expedited process via DCF. Not so with B2 and N600K, which is not treated as urgent unless the child is close to aging out at 18 years old.