So here is some information on your questions. Hopefully some of it will answer your questions.
Candidiasis of the Vagina (Vaginal Candidiasis, Vaginitis, or Yeast Infection)
Symptoms may include itching, burning, and pain around the vagina, labia (vaginal lips), or anal area and thick, whitish, sometimes curd-like vaginal discharge. Usually, you know when you have it. So it may be coming from another source not her vagina.