How do you say female cousin in Russian?

There isn't a single word for "female cousin" in Russian, like in English. You need to specify the relationship more precisely:

* If she's your mother's sister's daughter: двоюродная сестра (dvoyurodnaya sestra)

* If she's your father's brother's daughter: двоюродная сестра (dvoyurodnaya sestra)

* If she's your mother's brother's daughter: двоюродная сестра (dvoyurodnaya sestra)

* If she's your father's sister's daughter: двоюродная сестра (dvoyurodnaya sestra)

All of these translate to "female cousin" in English, but they emphasize the specific relation within the family.