She keeps talking about her birth mom, but also about all sorts of people who are no longer around (due to moving, job changes, and death).

that sounds like she is afraid of losing yet another person that she loves or cares for. If you want to find a family therapist, start looking in the phone book under counseling or family therapy. Ask for a therapist who specializes in working with adopted children. If they don't sound confident, ask for referrals.

You might also want to call your local psychiatric hospital and see if they provide services for children, that's another opportunity to find a referral.

best of luck!