Hi there. Here are a few good resources I looked at those first few weeks. Also, I highly recommend the book "Gifts" and "Babies With Down Syndrome: A New Parent's Guide."
National Down Syndrome Society: www.ndss.org
National Association For Down Syndrome: www.nads.org
Mayo Clinic Down syndrome info: https://www.mayoclinic.com/health/down-syndrome/DS00182
Also, whatever state she lives in will have a state Down syndrome society, and likely a Web site, that will have a lot of local resources. She should also contact the county she lives in about getting set up for Early Intervention services.