Desperate for help

Told my 11 year old daughter, her brothers and step brothers we were expecting a baby.

She's always had behavioral issues, but things have been getting better.

She absolutely lost it, screaming, angry, telling me she is leaving, she doesn't want this family and she hopes the baby dies...

I'm so distraught, I want to help her, I want to show her love and support but I feel so lost right now at her reaction, at her feelings towards it.

I'm desperate for advice...

(Need to preface this, she sees a psychologist twice a month and have her in several programs for mental health)

She has a beautiful heart and a kind soul, she's been through trauma that we are working through but when she has big emotions, she completely loses herself, behaves in a way that is not my daughter.