That is really unprofessional of her

You should talk to her supervisor and consult them if this is appropriate. You should make an appointment with her supervisor to make the supervisor aware of the situation. State that you are not comfortable working with her and her attitude made you feel that she is discriminating against a pregnant woman (do not mention the racial discrimination unless you have enough evidence ).

Politely ask for another HR representative to work with you. Talk to your supervisor about this event and also print out a copy of this email as prove.