Worried about sibling of ASD child

[Rizzlekicks]

Has anyone had their non-ASD child/ren see a counsellor/ psychologist? Our 8 yr old daughter is very angry and upset at the moment, saying that her ASD brother always gets his way and she doesn't. She will provoke him to hit her, then she screams, and he goes into meltdown. We are exhausted by it and very keen she sees someone as she is not in a happy place at the moment. We don't know what to do to make her happpy again.