Could be a number of things.
*Untreated STD
*Soap w/ perfumes & colorings
*Wearing panties of any material other than cotton
*BV from certain condom brands, lubes, or multiple men CIP
*Lazy hoe taking a "wash up", rubbing th rag between her labia but not her groins
*Lazy hoe not bathing at all
*Lazy hoe wearing dirty panties
*Drinking sodas = urine leakage = old pissy smelling pussy
*Douching
*Being young: if you've ever worked in direct patient care you know youngins do not know how to keep their ass clean
*Diet: I have garlic pussy sometimes