It is narrated from Sayyidah Umm Atiyyah (may Allah be pleased with her) that the Messenger of Allah (peace and blessings be upon him) said regarding the washing of his daughter: "Begin (the washing) with her right side and with the parts washed in ablution."
Hadith Referenceالمعجم الكبير للطبراني / مسند النساء / 21623