Daughter plays baby sister but I’m having a boy

Quick question! I’m having a boy in February and my daughter from day 1 has said it’s a girl and that’s sister. She was devastated when I told her it was a boy. She cried about it for two days. Now she constantly plays “baby sister” with her baby dolls and often calls our son a her. Is she just playing or is she still confused or upset? She has two girl dolls and one boy she takes around everywhere but she never calls him baby brother. She’s 3! I just wanna make sure she understands I’m having a boy!