I think it's normal for kids to like people who look/act like themselves. I don't know if it's really about race, or about having friends who look similar to them.
I grew up in extremely diverse areas my whole life. So, I never had any issues seeing dark kids and light kids all the same way.
But, I live in a town right now where there are very few blonde haired fair skin people, and in my daycare, I just got a brother sister duo with very light skin, red hair, and light blue eyes. I've had a few daycare kids ask why they look like that. They mean it very innocently, but someone says something at least once a week. They pet the baby's head and look at her eyes all the time because they are just kinda amazed.
I don't feel like it's a real problem, but I need to get them to quit mentioning it in front of them. (ideas are welcome here)
I think I might tell her that she can't say those things in front of her dark skinned friends. She can talk to you about it, but not in front of other kids. It's hurtful, and while you understand her feelings, it's not really ok to let anybody else know.