What Causes White Vaginal Discharge?

I am bhasin and I am chatting with u regarding of my sister's health actually she is 14yrs and she didn't get her first period she is worried and nervous her varginal discharged.... in her vargina something white cheessy things appears is this normal ...???her breasts is growing but her puberty hair is growing slowly.....is this a yeast problem can u give an situation