Best way to deal with a child with abandonment issues?

I know of a young girl (she’s 6) who was rejected by her biological mother. Her father remarried and he is now living with his new wife (her step-mom). Her father and step-mom have a son (who is 5). So, that would make him her half-brother.

The six year old girl doesn’t feel loved, and acts out a lot. Her step-mom finally got her set up with a counselor (starting next week).

Her biological Mom stopped talking to her in December..for no reason.