A girl with yellow water and itching down there may have vaginal inflammation as a symptom. There are more types of vaginitis, which means that the pathogens of the infection are different. You must go to the hospital and let the doctor check it and test the leucorrhoea and treat it according to the results of the leucorrhoea. In the case of trichomoniasis, metronidazole should be applied. If it is mycosis vaginalis, clotrimazole vaginal tablets should be placed vaginally. If it is bacterial vaginitis, it needs to be treated with oral clindamycin or metronidazole. You should pay attention to the hygiene of your vulva, wear cotton and breathable underwear, and both men and women should wash their vulva or wear condoms before and after sex to avoid cross-infection.