Hello, Yes baby can get fungus infection over vulva giving depigmented patch. Please do not worry as she is unlikely to have the virus in her system.
Milia is skin condition of newborns.
Cream would not give such patch except sunscreen one.
You could try a clotrimazol cream or lotion rubbing well for couple of weeks and see..
It looks more like a white spot rather than a patch. You know like a whitehead
You can upload a close-up snap using paper-clip like icon. Tenia infection is likely cause.